Add pddl-visualizer plugin (pure skill) + worked example

[omereliy]

Summary

Adds a fifth marketplace plugin, pddl-visualizer — a Tier‑1 pure skill (no MCP server, no Python deps) that turns a PDDL domain + problem + plan into a single self-contained, animated HTML file that opens offline in any browser.

This is a clean-room adaptation of the planning-visualizer university project. That project is a full web app (React + Node/Express + tRPC, Python/Fast Downward, runtime-compiled TypeScript renderers). We keep only its one novel idea — LLM-generated, domain-specific visualizers — and re-express it within this marketplace's model. No upstream code is reused.

Design (why a pure skill)

• No backend, no server, no build. The agent generates the HTML directly; output is one offline file (inline SVG + JS). This is the deliberate simplification of the source app's multi-service stack.
• Reuses sibling plugins as soft dependencies, no cross-plugin imports:
  • pddl-parser get_trajectory → ground-truth state at each step (the skill never hand-simulates state).
  • pddl-solver classic_planner / numeric_planner → obtain a plan when the user has none.
• Generic graph mode renders any domain (objects → nodes, binary predicates → edges, unary → badges, per-step fact diff); optional themed mode for familiar domains (blocksworld, logistics, gripper).
• Mirrors the existing pure-skill plugin pddl-author in structure and conventions.

Worked example

plugins/pddl-visualizer/examples/ contains a tiny logistics instance and the generated logistics-plan.html. Its per-step states were produced by pddl-parser's get_trajectory (unified-planning backend, 4 steps) — not hand-written — and the README documents how to regenerate.

Correctness note

While wiring the skill I verified the real get_trajectory contract: it assumes the plan is valid and returns no per-step verdict. The skill reflects this — an invalid plan makes the tool error, at which point it stops and defers to pddl-validator rather than fabricating frames.

Footprint

• New: plugins/pddl-visualizer/{.claude-plugin/plugin.json, CLAUDE.md, skills/pddl-visualizing/SKILL.md} + examples/
• Edited: both marketplace catalogs (entry + metadata 1.5.0 → 1.6.0), root CLAUDE.md listing
• Skills-only plugin → correctly omits .mcp.json / .claude/settings.json / tests/

Verification

• tests/static_checks.py → all checks pass
• Embedded JS in the example → node --check clean
• Reviewed by the repo's simplifier agent; flagged items (unused Read perm, missing tool-signatures section, failure-handling framing) all addressed.

No license was reused from the upstream repo (it ships none); this is an independent implementation of the concept.

https://claude.ai/code/session_01Q3Gyj9LRouEoSzGzfBy6c4

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