Docs: collision-fidelity pass record + MeshCollider Read/Write gotcha + guardian harness pattern

Session log Part C (execution + validation evidence), roadmap stabilize #2
ticked, CLAUDE.md gains the MeshCollider-bakes-only-if-Read/Write gotcha
(38.4 KB, in budget), validation-harness.md gains the EditorApplication.update
guardian + EditorPrefs handoff pattern.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.claude/skills/dots-dev/references/validation-harness.md

@@ -63,6 +63,12 @@ DOES propagate into parented children's `LocalToWorld` (verified live on 6.5.0).
   and tears down the room.
 - Therefore: **capture evidence in the SAME `execute_code` call that first detects the condition** (e.g.
   `enemies>0`) — a separate "then screenshot" round-trip loses the window.
+- **Multi-sample observations (movement deltas, before/after) that can't fit one call: install an
+  `EditorApplication.update` guardian delegate** (proven 2026-07-09, enemy-backstop smoke). The closure runs every
+  editor frame: it can out-race damage (`Health.Current = Max` per frame — beats the respawn-reset trap above),
+  park the player, take timed snapshots, and stash results in `EditorPrefs` (survives across `execute_code`
+  calls — statics do NOT). Always: wrap the body in try/catch that UNSUBSCRIBES on error, add a hard timeout
+  unsubscribe (~90 s), self-unsubscribe when done, and delete the `EditorPrefs` keys after reading them.
 - Prefer the server-inject harness above whenever the question doesn't actually require a live run.
 
 ## Visual/asset verification limits