before_agent_start handler appends the trunk-based git law to the system
prompt only when cwd is under ~/Projects/. Hard cwd scope because every
context-file provider resolves at or below the repo root - an ancestor
AGENTS.md is never loaded by descendant repos. Verified live: quote probe
fires under serverAppConfig, silent in /tmp and ~/.omp. Fires for subagent
sessions too (shared cwd). Changelog entry added.