fix(langs): declare all language packages as explicit dependencies

[EurFelux]

Summary

• gen-langs-map.cjs now auto-syncs package.json dependencies after generating src/index.ts, ensuring every imported package is explicitly declared
• Moved @codemirror/language-data from dependencies to devDependencies and pinned to 6.5.2 (only used as gen script input, not at runtime)
• Removed @codemirror/language-data from peerDependencies

Problem

The generated src/index.ts imports from 20+ @codemirror/lang-* and @codemirror/legacy-modes packages that were never declared in package.json. They only worked as phantom dependencies hoisted from @codemirror/language-data, which breaks under pnpm strict mode.

Fixes #754
Fixes #759

Note on src/index.ts diff

The regenerated src/index.ts includes minor content changes (e.g. jinja upgraded from legacy mode to @codemirror/lang-jinja, new xq/xqm/xqy extensions added) because the repo has no lockfile — npm install resolved @codemirror/language-data@6.5.2 while the previously committed output was generated from 6.5.1. This version has now been pinned to 6.5.2 in devDependencies to prevent future drift.

Test plan

• Run npm run gen in extensions/langs/ and verify package.json dependencies are auto-updated
• Verify all imports in src/index.ts have corresponding entries in package.json
• Test with pnpm install --strict-peer-dependencies to confirm no phantom dependency issues

🤖 Generated with Claude Code