Patch reflection-preflight.sh Check 3+4 window for pre-write tool-call tolerance

ROOT CAUSE: The 2026-06-23 LEARNINGS structural fix (issue tool calls BEFORE writing reflection bulk text) puts task creation events 1-3 minutes BEFORE the reflection file mtime. The current canary window is [REFL_MTIME, REFL_MTIME + 30min] — tasks created BEFORE mtime are excluded → false-positive ALERT. Observed 2026-06-25: both P1 (2d9e42f9 at 04:02:16Z) and P2 (dd5270b7 at 04:02:07Z) from 2026-06-24 reflection completed successfully, but the memory file mtime was 04:04:00Z, so canary Check 3 and Check 4 excluded both and fired 2 false-positive ALERTs. DELIVERABLE: Patch the window in scripts/reflection-preflight.sh Check 3 + Check 4 to: WINDOW_START = REFL_MTIME - 600 (10 min BEFORE mtime) WINDOW_END = REFL_MTIME + 1800 (30 min AFTER mtime, unchanged) VERIFICATION: scripts/reflection-preflight.sh returns zero ALERTs against the current state of memory/2026-06-24.md. Add a regression test that fixtures tasks-before-mtime. SCOPE GUARDRAIL: only modify scripts/reflection-preflight.sh and scripts/test-canary-check-*.sh.