Phase 1.2: Build Tooling Modernization (#203)

* add feature branch audit file

* build: modernize build tooling for Phase 1.2

- Add [tool.ruff] configuration (replaces flake8 and black)
- Remove [tool.flake8] configuration
- Remove [tool.tox] configuration (justfile replaces tox)
- Remove flake8, tox, black, tox-gh-actions from dev dependencies
- Minimize setup.py to shim for backwards compatibility
- Fix justfile references (autobahn -> txaio)
- Apply ruff autoformat to source files (minor whitespace cleanups)
- Add project header banner to justfile default recipe
- Add missing docstring to docs-view recipe

Verified recipes on all environments (cpy314, cpy313, cpy312, cpy311, pypy311):
- just version-all: All venvs reported
- just create-all: All venvs created
- just install-all: Package installed in all venvs
- just install-tools-all: Dev tools installed in all venvs
- just check-format cpy311: All checks passed
- just check-typing cpy311: 34 errors (pre-existing technical debt)
- just test cpy311: 104 passed, 14 skipped
- just test pypy311: 104 passed, 14 skipped
- just build cpy311: Successfully built wheel and tarball
- just docs cpy311: Build succeeded
- just autoformat cpy311: Applied cleanups

Closes #202

* build: add standardized build recipes to justfile

Add consistent build recipes that will be shared across all WAMP repos:
- build: Build wheel package
- build-all: Build wheels for all environments (single for pure Python)
- build-sourcedist: Build source distribution
- clean-build: Clean build artifacts
- verify-wheels: Verify wheels using twine check
- publish: Now depends on build, build-sourcedist, and verify-wheels

For pure Python packages like txaio, build-all only builds one universal
wheel. For native extension packages (autobahn-python, zlmdb), build-all
will build per-environment wheels.

* build: clarify verify-wheels for pure Python vs native packages

Add note explaining that auditwheel is not applicable for pure Python
packages (py3-none-any wheels). auditwheel checks binary compatibility
and is used for native extension packages like autobahn-python and zlmdb.

* build: Add missing common justfile recipes for ecosystem consistency

Added recipes:
- fix-format: renamed from autoformat (autoformat kept as alias)
- test-all: run tests on all environments
- upgrade: upgrade dependencies in single environment
- upgrade-all: upgrade dependencies in all environments
- publish-pypi: download from GitHub and publish to PyPI
- publish-rtd: trigger Read the Docs build
- download-github-release: download release artifacts from GitHub

These recipes align txaio with the common justfile recipes specification
defined in MODERNIZATION.md for consistent developer experience across
the WAMP Python ecosystem.

* build: Modernize to src layout with Furo/MyST/AutoAPI docs

- Migrate from flat layout to src layout (txaio/ -> src/txaio/)
- Rename test directory (test/ -> tests/)
- Add py.typed marker for PEP 561 compliance
- Modernize docs/conf.py with Furo theme, MyST Markdown, sphinx-autoapi
- Add .readthedocs.yaml for RTD builds with [docs] extra
- Update pyproject.toml with separate [docs] and [dev] extras
- Update justfile paths for src layout, add install-docs recipe
- Delete legacy files: setup.py, MANIFEST.in, deploy.sh, versions.sh

* docs: Fix symlinks to wamp-ai submodule, update index.rst

- Update .ai submodule to include audit docs in audit/ folder
- Fix docs symlinks to point to .ai/ instead of .audit/:
  - AI_AUDIT_PROCESS.md -> .ai/audit/AI_AUDIT_PROCESS.md
  - AI_AUDIT_PROCESS_REVIEW.md -> .ai/audit/AI_AUDIT_PROCESS_REVIEW.md
  - AI_POLICY.md -> .ai/AI_POLICY.md
  - CLAUDE.md -> .ai/AI_GUIDELINES.md
- Remove docs/OVERVIEW.md and docs/README.md symlinks (not needed)
- Update index.rst with proper structure and AI Policy section

* docs: Move AI docs to docs/ai/ subfolder

Reorganize AI-related documentation into dedicated subfolder:
- Create docs/ai/ directory for all AI policy documents
- Add symlinks to wamp-ai submodule:
  - ai/AI_POLICY.md → .ai/AI_POLICY.md
  - ai/AI_GUIDELINES.md → .ai/AI_GUIDELINES.md
  - ai/AI_AUDIT_FILE.md → .ai/audit/AI_AUDIT_FILE.md
  - ai/AI_AUDIT_PROCESS.md → .ai/audit/AI_AUDIT_PROCESS.md
  - ai/AI_AUDIT_PROCESS_REVIEW.md → .ai/audit/AI_AUDIT_PROCESS_REVIEW.md
- Remove old symlinks from docs/ root
- Update index.rst to reference ai/ subfolder

This keeps AI meta-documentation separate from technical docs
and follows consistent structure across WAMP repos.

* chore: Bump version to 25.12.1

Note: This work was completed with AI assistance (Claude Code).

Author: oberstet

.ai

@@ -0,0 +1,8 @@
+- [ ] I did **not** use any AI-assistance tools to help create this pull request.
+- [x] I **did** use AI-assistance tools to *help* create this pull request.
+- [x] I have read, understood and followed the project's AI_POLICY.md when creating code, documentation etc. for this pull request.
+
+Submitted by: @oberstet
+Date: 2025-11-25
+Related issue(s): #202
+Branch: oberstet:modernization-phase-1.2

.audit/oberstet_modernization-phase-12.md

@@ -0,0 +1,26 @@
+# .readthedocs.yaml
+# Read the Docs configuration file for txaio
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html
+
+version: 2
+
+build:
+  os: ubuntu-24.04
+  tools:
+    python: "3.11"
+  # Install system packages for spell checking
+  apt_packages:
+    - libenchant-2-2
+
+sphinx:
+  configuration: docs/conf.py
+  builder: html
+  fail_on_warning: false
+
+python:
+  install:
+    # Install the package with docs dependencies
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs