Add metatest to verify template capabilities against minja
Cross-checks declared test capabilities (ToolSupport, ThinkingSupport) against
minja's runtime detection. Tools mismatches are hard failures; thinking mismatches
are informational since minja's detection is heuristic.
Also adds TODO references to minja#20 for future capability detection improvements.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
