feat: add CodeBuddy platform support

[songsjl]

Summary

Add native CodeBuddy support: introduce a .codebuddy-plugin/plugin.json
plugin manifest so CodeBuddy IDE / CodeBuddy Code auto-discover the plugin
when the repo is cloned, and register codebuddy as an installable platform
in install.sh / install.ps1 (skills link into ~/.codebuddy/skills).
Documentation updated across README.md, all 7 localized READMEs, the
homepage install section, and the CLAUDE.md version-sync list.

Linked issue(s)

How I tested this

• pnpm lint
• pnpm --filter @understand-anything/core test
• pnpm test
• Manual smoke test (describe above)

Local verification (Node 22.14.0 / pnpm 10.6.2, matching the
packageManager pin):

• pnpm lint — 0 ESLint errors
• pnpm --filter @understand-anything/core test — 46 files / 976 tests passed
• pnpm test — all assertions pass (490+ passed, 15 skipped). A single
  vitest worker timeout occurred under full-suite concurrency on Windows;
  the affected file (test_extract_import_map.test.mjs) passes 60/60 in
  isolation. No source or test files are touched by this PR.
• understand-anything-plugin/.codebuddy-plugin/plugin.json validated as
  well-formed JSON, matching the existing .claude-plugin/plugin.json shape
• install.ps1 parses cleanly (PowerShell syntax parser)
• install.sh / install.ps1 platform tables dry-run checked
  (codebuddy → ~/.codebuddy/skills, per-skill style)
• All 8 READMEs (en + 7 locales) updated consistently; each shows the new
  CodeBuddy row and installation section

Versioning

• Version bumped in all five manifests, OR
• N/A — internal/docs-only change