Docs: session log Part P + roadmap tick + CLAUDE.md gotcha — Phase 1.5b decals bundle shipped

Bundle 2 (decals): explosion scorch pool, cover damage-cracks, room-arena
scars — all procedural, client-only, zero netcode. Records the pivotal
finding that a stock Synty prop shadergraph's _BaseColor is Unity-Per-Material
(not Hybrid-Per-Instance), so URPMaterialPropertyBaseColor darkening silently
no-ops on cover — the fork to decal quads.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -319,14 +319,50 @@ normals untouched. Ground luminance now 0.30/0.33 in edit ambient (tints stay th
 for the play lap). Recipe note: bake pattern = readback-blit sources to linear Color[] → composite →
 LinearToGammaSpace → PNG sRGB; HP detail imports LINEAR.
 
+## Part P — Phase 1.5b bundle 2 (DECALS) shipped
+
+Three locked sub-features, all **client-only presentation, procedural, zero netcode surface** (they read
+*existing* replicated state): (a) explosion scorch pool, (b) cover damage-cracks, (c) light room-arena scars.
+
+- **Pivotal grounding finding (a fork the roadmap didn't foresee):** the roadmap specified cover cracks as
+  `URPMaterialPropertyBaseColor` darkening — but that would **silently no-op**. Cover's render child uses the
+  Synty `Generic_Basic.shadergraph`, whose `_BaseColor` is declared **Unity-Per-Material**
+  (`overrideHLSLDeclaration:false`, `hlslDeclarationOverride:0`), **NOT Hybrid-Per-Instance** — so the
+  Entities-Graphics per-instance override that `EnemyHitFlashSystem` drives (enemies use the DOTS-authored
+  `AnimatedLitShader`, which IS hybrid-per-instance) writes to a slot the shader never reads. Exactly the
+  "dark render masks a material bug" trap. **Operator fork → crack-decal QUADS** (guaranteed to render,
+  on-theme for a decals bundle, most legible as damage) + **light room-arena cracks** (skip base POIs — Part O
+  already baked their wear; the deleted-WornPath double-darken lesson).
+- **Architecture — one procedural decal primitive:** `FeedbackFx` gained `MakeDecalMaterial` (Sprites/Default,
+  ZWrite off, transparent, vertex×MPB `_Color`), `BuildScorchMesh` (irregular soft radial disc, vertex α1→0
+  jittered rim — the feathered edge is what stops it ghosting over fog like the old rectangle quad) and
+  `BuildCrackMesh` (jagged radial spokes, feathered tips). `ScorchDecalSystem` = static `RequestScorch(pos,
+  radius)` queue → pooled fading discs under a `DontDestroyOnLoad` root, scene-gated "Game", per-decal
+  hold→fade via a reused MPB (mirrors `DynamicLightSystem.RequestFlash`); wired from `WorldFeedbackSystem`'s
+  barrel-boom branch; **reusable by the bundle-3 geyser**. `CoverDamageSystem` accretes cracks keyed on
+  replicated `BlightClutter.Remaining` (Variant 4, 8→0) + shatter-scorch on despawn. `RoomDressingSystem` lays
+  arena scars on a distinct hash sub-stream (0xD2E56), torn down with dressing. `DecalConfig` = live knobs.
+- **Self-review caught + fixed (stood in for the diff-review — client-only, no netcode):** the shatter-scorch
+  is now **proximity-gated** (mirrors WorldFeedbackSystem) — else a room-teardown / region-transit despawn
+  storm (every cover ghost dropped at once, off-camera) would spray scorches and exhaust the 24-cap pool.
+- **Verified:** 470/470 EditMode; console clean (only pre-existing `WorldAtmosphereSystem` CS0618 warnings —
+  not this bundle). L3 headless — all 3 systems exception-free in ClientWorld, `DecalConfig` reset correct,
+  and the flagship scorch path proven end-to-end via VALUE inspection (mesh 25 verts + feathered vColors,
+  y=0.05, scale 2.76 = 3.25×0.85 exact, Sprites/Default queue 3000, shadows off, `_Color` dark-char @ α0.85)
+  **plus** the full spawn→hold→fade→recycle→pooled-reuse lifecycle (no leak). Commit `<pending>`.
+- **Deferred to the operator's gate lap (documented, per precedent):** the in-run VISUAL judgment — cover
+  cracks accreting during real carving, arena scars in a real room, and whether the dark scorch reads well
+  over the dark baked ground — needs a launched expedition + a focused editor (unfocused blocks live-frame
+  verify). Knobs to taste on the lap: `ScorchColor`/alpha, `CoverCrackMaxCount`, `RoomArenaDecalCount`.
+
 ## Next-session intent
 
-**Phase 1.5b bundle 1 (ground) is SHIPPED**; remaining locked bundles in order: **2) decals** (explosion
-scorch pool · POI grime · cover damage-cracks) → **3) Blight geyser** (mini design review first — new
-replicated erupt-phase surface) → **4) critters + weather beats**. Then the operator's 1.5 gate lap ("no
-longer static", ground judged explicitly) → Phase 1.7 boon overhaul (design-review-FIRST) → Phase 2
-hub-ification. Taste queue: arid brightness · craters call · B5 split-panels smoke · barrel explosion VFX
-polish · flower density judgment (base may read dense — operator call on the lap).
+**Phase 1.5b bundles 1 (ground) + 2 (decals) are SHIPPED**; remaining locked bundles in order: **3) Blight
+geyser** (mini design review FIRST — new replicated erupt-phase surface) → **4) critters + weather beats**.
+Then the operator's 1.5 gate lap ("no longer static", ground + decals judged explicitly) → Phase 1.7 boon
+overhaul (design-review-FIRST) → Phase 2 hub-ification. Taste queue: **decals feel lap (scorch/crack/scar
+tuning)** · arid brightness · craters call · B5 split-panels smoke · barrel explosion VFX polish · flower
+density judgment (base may read dense — operator call on the lap).
 
 Related: [[Iteration_2026-07_CoopHades]] · [[2026-07-07_Workflow_Consolidation]] ·
 [[2026-07-07_Expedition_Enemy_Stuck_Harvest_Feedback]]