fix(installer): include codegraph_files in Claude auto-allow (#565)

[ruanchaves]

Summary

Closes #565.

The Claude installer's auto-allow list omitted mcp__codegraph__codegraph_files, so codegraph install --target=claude ... wrote a settings.json that still prompted for codegraph_files even though the documented manual Claude example already includes it.

Change

• add mcp__codegraph__codegraph_files to getCodeGraphPermissions() in src/installer/targets/shared.ts
• add one installer regression assertion in __tests__/installer-targets.test.ts
• add an [Unreleased] fix note to CHANGELOG.md

This PR is intentionally narrow. It does not expand the Claude allowlist to codegraph_explore or codegraph_trace; those can be discussed separately.

Validation

• npx vitest run __tests__/installer-targets.test.ts
• npm run build