Initial import: JGraphT algorithm visualizations

Self-contained, single-page HTML visualizations of graph algorithms
implemented in JGraphT. Migrated from
seilat/jgrapht @ visualizations branch (12 commits squashed into
this initial import).

Layout flattened: files previously under visualizations/ now sit at
repo root so GitHub Pages and the Docker image serve from /.

Modes covered:
  - K-shortest paths (Yen) — pickable pane A/B from five algorithms:
    Yen+Dijkstra, Yen+A*, BPYen+Dijkstra, BPYen+A*, Eppstein.
  - Single shortest path — Dijkstra vs A* with reverse-Dijkstra
    heuristic.
  - All paths — AllDirectedPaths backward-BFS baseline vs forward
    pruning (the "sandwich" gate: forward-reachability + budget).

Dual-licensed LGPL-2.1-or-later OR EPL-2.0, matching JGraphT.

Author: seilat

.dockerignore

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+.git
+.github
+.gitignore
+.nojekyll
+README.md
+CONTRIBUTING.md
+CODE_OF_CONDUCT.md
+license-EPL.txt
+license-LGPL.txt
+docker-compose.yml
+.dockerignore
+vercel.json

.github/workflows/pages.yml

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+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          # Publish the repo root as the site. .nojekyll disables Jekyll.
+          path: '.'
+
+      - name: Deploy
+        id: deployment
+        uses: actions/deploy-pages@v4

.gitignore

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+# OS / editor noise
+.DS_Store
+Thumbs.db
+*.swp
+.idea/
+.vscode/
+*.iml
+
+# Local dev servers / dumps
+node_modules/
+.cache/
+.tmp/
+*.log

.nojekyll

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+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and committers pledge to making participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, sex characteristics, gender identity and expression,
+level of experience, education, socio-economic status, nationality, personal
+appearance, race, religion, or sexual identity and orientation.
+
+## Our Standards
+
+Examples of behavior that contributes to creating a positive environment
+include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+* Proactively reading, following, and improving community guidelines
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or
+ advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic
+ address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+ professional setting
+
+## Our Responsibilities
+
+Project committers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
+
+Project committers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+## Contribution Model
+
+In the JGraphT project, we use the term "committers" rather than "maintainers".
+
+This is because other than release management, most project maintenance is done through contributions,
+rather than through work carried out by a dedicated team.  Committers
+help contributors carry this out through processes such as issue discussions
+and code review.  Committers generally do not even commit their own work directly;
+instead, they wait for another committer to review and merge their contributions.
+
+Understanding and respecting these roles is an important aspect of our
+code of conduct.
+
+## Scope
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community. Examples of
+representing a project or community include using an official project e-mail
+address, posting via an official social media account, or acting as an appointed
+representative at an online or offline event. Representation of a project may be
+further defined and clarified by project committers.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at admin@jgrapht.org. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
+
+Project committers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at https://www.contributor-covenant.org/version/1/4/code-of-conduct.html
+
+[homepage]: https://www.contributor-covenant.org
+
+For answers to common questions about this code of conduct, see
+https://www.contributor-covenant.org/faq

CODE_OF_CONDUCT.md

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+# Contributing
+
+Thanks for your interest in improving the JGraphT algorithm visualizations.
+
+## Where to discuss
+
+Before opening a non-trivial PR, please post a short heads-up to the
+[`jgrapht-dev` Google Group](https://groups.google.com/g/jgrapht-dev) with a
+link to your branch. This is the same convention used by the main
+[JGraphT][jgrapht] repository — it keeps the contributor pool small enough that
+async review on the list works well.
+
+For bug reports and small fixes, a GitHub issue or PR is fine.
+
+We follow the [JGraphT Code of Conduct](CODE_OF_CONDUCT.md).
+
+[jgrapht]: https://github.com/jgrapht/jgrapht
+
+## What fits in this repository
+
+This repo hosts **interactive teaching visualizations** of algorithms that are
+implemented (or being proposed) in JGraphT. Good fits:
+
+- A new algorithm pair (baseline vs. variant) that can be stepped through
+  side by side and explained event-by-event.
+- A new graph example that exposes a subtle correctness or performance edge
+  case in an existing visualization.
+- UX polish: clearer per-step explanations, glossary entries, accessibility
+  fixes, layout improvements.
+
+What does **not** fit:
+
+- Full Java/JGraphT algorithm code — that belongs in
+  [`jgrapht/jgrapht`](https://github.com/jgrapht/jgrapht).
+- Pure benchmarking infrastructure — also belongs in the main repository.
+- Animations of algorithms that are not in (or proposed for) JGraphT.
+
+## Design constraints
+
+The page is intentionally a single self-contained HTML file (HTML + inline CSS
++ inline JS, no external dependencies, no build step). This keeps the deploy
+surface tiny. PRs that add external runtime
+dependencies will need a strong motivation; please raise on the mailing list
+first.
+
+It is acceptable for the file to grow, but please:
+
+- Keep all event-driven animation work behind a step queue (don't `setTimeout`
+  ad-hoc) — match the existing pattern.
+- Keep per-step explanations short and accurate; if an explanation is wrong
+  on any example, that's a correctness bug.
+- Match the existing colour / pane / glossary conventions so that modes feel
+  consistent.
+
+## Pull request checklist
+
+- [ ] I posted a heads-up on `jgrapht-dev` for non-trivial changes.
+- [ ] The page still opens cleanly in modern Chrome / Firefox / Safari from a
+      plain `file://` path **and** via `python -m http.server`.
+- [ ] All animation steps display a non-empty, accurate explanation.
+- [ ] If I added a new algorithm pair, the two panes agree on optimal-path
+      sets (with the documented Yen tie-break caveat) on every supplied
+      example.
+- [ ] No new external runtime dependencies (or I've discussed them on
+      `jgrapht-dev` first).
+- [ ] My commit messages follow Conventional Commits
+      (`feat: ...`, `fix: ...`, `docs: ...`, `chore: ...`, `refactor: ...`).
+      Scope is optional but should be the algorithm or mode when it helps
+      (e.g. `feat(eppstein): ...`, `fix(forward-pruning): ...`).
+
+## License
+
+By contributing, you agree that your contributions will be dual-licensed under
+the same terms as the project itself:
+
+- GNU Lesser General Public License (LGPL) 2.1
+- Eclipse Public License (EPL) 2.0
+
+`SPDX-License-Identifier: LGPL-2.1-or-later OR EPL-2.0`

CONTRIBUTING.md

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+# JGraphT algorithm visualizations: Yen / Eppstein K-shortest paths,
+# Dijkstra vs A*, and AllDirectedPaths forward pruning. Single
+# self-contained HTML file served by nginx-alpine.
+FROM nginx:1.27-alpine
+
+# Run as non-root for safer deployment.
+RUN addgroup -S app && adduser -S -G app app \
+    && touch /var/run/nginx.pid \
+    && chown -R app:app /var/cache/nginx /var/run/nginx.pid /usr/share/nginx/html /etc/nginx/conf.d
+
+COPY --chown=app:app index.html /usr/share/nginx/html/index.html
+COPY --chown=app:app favicon.ico /usr/share/nginx/html/favicon.ico
+COPY --chown=app:app apple-touch-icon.png /usr/share/nginx/html/apple-touch-icon.png
+COPY --chown=app:app nginx.conf /etc/nginx/conf.d/default.conf
+
+USER app
+
+EXPOSE 8080
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+    CMD wget -q --spider http://127.0.0.1:8080/ || exit 1
+
+CMD ["nginx", "-g", "daemon off;"]