chore: consolidate agent packaging

[hadrien]

Problem

• Portable plugin payload and local agent configuration share repository-root namespaces.
• Claude and Codex instructions duplicate generated Beads content and drift independently.
• The MkDocs theme template occupies an unrelated top-level directory.

Solution

• Move the shared Claude and Codex package to plugins/fastsqla.
• Update native marketplace catalogs and Context7 paths for the new plugin root.
• Remove empty Claude settings, Codex Beads hooks, and the bundled local Beads skill.
• Make CLAUDE.md import canonical AGENTS.md across platforms.
• Move the MkDocs override under .github while preserving rendered output.
• Verify native validators, real installs, strict docs, Ruff, and pytest.

fs-1rc.4

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.36%. Comparing base (11858db) to head (bcdd82c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #113   +/-   ##
=======================================
  Coverage   97.36%   97.36%           
=======================================
  Files           1        1           
  Lines         114      114           
  Branches        2        2           
=======================================
  Hits          111      111           
  Misses          3        3           

Flag	Coverage Δ
fastapi-post121	97.36% <ø> (ø)
fastapi-pre121	97.36% <ø> (ø)
sqlmodel	97.36% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

[hadrien]

Independent review found one portability issue: a Git symlink may become a plain text file on Windows when core.symlinks=false. Replaced the symlink with Claude Code’s supported one-line @AGENTS.md import and pushed bcdd82c. The reviewer reported no other findings.