Adds /add-gcal-tool — a sibling of /add-gmail-tool that installs
@cocal/google-calendar-mcp with the same OneCLI stub-file pattern. Skill
applies the Dockerfile + TOOL_ALLOWLIST changes at install time; trunk
stays clean so users who never run the skill don't carry the calendar
MCP in their image.
Dropped the Phase 5 dry-run section since it hardcoded a per-install
image tag slug and duplicated Phase 4's live agent test.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
