chore: update Angular to 21.2.0 and bump minor dependencies (#60)

Closes #58

- Angular packages: 21.1.x → 21.2.0
- @codemirror/language: 6.12.1 → 6.12.2
- vitest: 4.0.8 → 4.0.18
- typescript: 5.9.2 → 5.9.3
- rxjs: 7.8.0 → 7.8.2
- tslib: 2.3.0 → 2.8.1
- bun packageManager: 1.3.8 → 1.3.10

jsdom v28 major bump deferred for separate evaluation.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: corvid-agent