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>

Docs/Vault/07_Sessions/2026/2026-07-09_B4d_Tail_Collision_Grounding.md

@@ -64,11 +64,51 @@ RPC / ordering surface**). Validation ladder: baked `CollisionWorld` raycast sam
 enemy backstop re-validation (spawned Husks near refit cover keep moving — the Depenetrate/tangent-slide
 was tuned on the OLD shapes) · suite + operator feel pass.
 
+## Part C — collision-fidelity pass EXECUTED (gate approved: full plan + large-solid-prop adds)
+
+**Built `Assets/_Project/Scripts/Editor/ColliderFitTools.cs`** (menu + programmatic Audit/Apply; idempotent —
+regenerates ring segments + prop adds from the current visuals each run) and applied it to the subscene:
+
+- **Rings REBUILT at fine resolution**: 16/24/24 coarse segments → **54/82/82** (~3.5-4 u arcs), each segment's
+  inner face fitted to the innermost TORSO-band (y 0.9–2.5) cliff vertex in its arc. Two audit-driven corrections:
+  (1) the 0.2–3.0 walk band chased shin-high cliff *skirts* and pulled the base wall 30→24.75 flat, stranding
+  playable meadow; (2) at coarse arcs one jutting rock walled off a whole 12–14 u span — hence torso band + fine
+  arcs. Result: base wall tracks 22.1–29.7 (avg 25.1), expedition 44.5–51.2 (avg 47.6), zero clamps/no-samples.
+- **Cover rocks**: 8 uniform boxes (4.2×4.2, axis-aligned) → **convex `MeshCollider`s of the actual
+  `CoverRock_*` render meshes** at the visuals' exact TRS.
+- **Landmarks**: hint-matched claim-once OBB fits (first audit's nearest-largest heuristic double-claimed the
+  cabin for `LM_WaterWheel` and gave `LM_Sign` a tent). Cabin 6×6→5.8×8.1, Tent 4×4→4.5×4.5 (walk-into-building
+  fixed); Well 3×3→1.9×2.0, Sign 2×2→0.6×0.5, Artefact 3×3→2.4×1.5 (invisible walls removed); Warpgate
+  8×2.5→8.3×6.8.
+- **Adds (approved fork)**: 11 colliders on previously walk-through solid props gated by the LOCAL fitted wall
+  radius at each prop's angle — 1 meadow-tree trunk capsule + 2 sci-fi crates (base), wind-turbine poles ×2,
+  satellite dish, solar rig ×2 per survey camp (both expedition slots). 50 rim-decoration trees correctly
+  excluded (they stand in the cliff transition zone behind the fitted wall).
+- **Spawn-safety pre-check**: player ring 2.5, wave ring 16, zone ring 14, room scatter ≤24, portal offset 5 —
+  all far inside every fitted wall; nothing gameplay-critical sits in the moved band.
+
+**New build gotcha (now in CLAUDE.md): a `MeshCollider` bakes ONLY if the mesh has Read/Write enabled** — the
+first Play after Apply threw `InvalidOperationException` per bake and produced NO cover shapes (0/6 solid in the
+baked `CollisionWorld`) while the classic scene view showed the colliders fine. Fixed by flipping `isReadable`
+on `SM_Env_Rocks_Spikey_03.fbx` + `SM_Env_Rock_06.fbx` (PNB_Arid_Desert) → 8/8 solid.
+
+**Validation (all passed):**
+- Baked-`CollisionWorld` probe (server): ring closure 32/32 rays per region inside the fitted band (expedition
+  44.1–50.6; base ≤28.5, short hits = Core/crate structures); cabin solid at its true footprint; well
+  1.7 u off-center FREE (old invisible wall gone); cover hulls 8/8 solid; **server==client static-body parity
+  (249 each)**.
+- **Enemy stuck-fix backstop re-validated live**: an `EditorApplication.update` guardian delegate (new
+  harness pattern → validation-harness.md) kept the AFK player alive + parked across the room, embedded enemy
+  E5041 at the exact center of a cover hull, and took timed snapshots: E5041 was **depenetrated out of the hull
+  and moving** (993.00,6.00 → 991.26,5.80 in ~4 s), the other 4 enemies converged normally around cover to the
+  parked player. No freezes.
+- EditMode suite green + console clean post-fix (bake exceptions gone).
+
 ## Next-session intent
 
-Execute the collision-fidelity pass per the gate answer → lighting/atmosphere pass → art-look decision
-gate (pixel filter ON/OFF side-by-sides). The B5 split-panels focused Play VISUAL smoke is still pending
-operator eyes (unfocused editor can't drive it).
+Phase 1.5 continues: lighting/atmosphere pass → art-look decision gate (pixel filter ON/OFF side-by-sides).
+Operator: eyeball the refit walls + cover rocks + new prop colliders in a real lap (fidelity is numeric-verified,
+feel is not), plus the still-pending B5 split-panels visual smoke.
 
 Related: [[Iteration_2026-07_CoopHades]] · [[2026-07-07_Workflow_Consolidation]] ·
 [[2026-07-07_Expedition_Enemy_Stuck_Harvest_Feedback]]