docs(overhaul): contract S4 c3b deletions

docs/research/2026-09-01-overhaul/2026-09-04-s4-handoff.md

@@ -159,10 +159,12 @@ memory −17.7 MiB. G3/G4 remain unpassed.
 
 ## 4. After chunk 2
 
-1. **S4-c3a is LANDED; c3b is unlocked.** Packet §21 records the owner's
+1. **S4-c3a is LANDED; c3b is contracted in packet §22.** Packet §21 records the owner's
    evidence-only exception, the exact mutation correction, narrow independent
    PASS, campaign commit mapping, and fresh build/focused gates. Write c3b's
-   deletion-only contract from the landed code. Do not start G3 until c3b lands.
+   deletion-only contract from the landed code. §22 deletes only dead grouped
+   sort-center/camera sidecars and preserves the live c3a keys. Do not start G3
+   until c3b lands.
 2. **G3 — S4's owner gate:** the lead runs `route-g3.txt` (13 matrix shots),
    `route-g3b.txt` (the capture poses; pose 15 now outdoors), `route-g3c.txt`
    (Nanto ×3, 300 s waits) with `pwsh -File tools/overhaul-selfgate/run-selfgate.ps1 -Label <l> -Route <file>`

docs/research/2026-09-01-overhaul/s4-depth-alpha-packet.md

@@ -1851,3 +1851,142 @@ allocation pins 2/2 at 0 B; shader/manifest/SPIR-V lane 32/32; `git diff
 --check` clean. The campaign `src`/`tests` tree is byte-identical to reviewed
 scratch commit `9cfddf301`. No graphical client was launched. c3b is now
 unlocked; G3 remains locked until the deletion-only c3b chunk lands.
+
+## 22. S4-c3b contract — delete the superseded alpha-order sidecars (lead, 2026-09-04)
+
+### 22.1 Retail and landed-code boundary
+
+This chunk changes no retail-visible renderer behavior. Named retail
+`D3DPolyRender::AddMeshToAlphaList @0x0059C230` accepts mesh/subset/surface and
+list-state flags but no camera or distance argument; it appends into one of two
+fixed arrays. `FlushAlphaList @0x0059D2E0` replays those arrays by index.
+Retail's only relevant distance step is earlier and per cell:
+`CShadowPart::insertion_sort @0x006B5130..0x006B519D`, before the resulting
+parts call `DrawMesh`. The paired bytes and the named pseudo-C agree on those
+facts; §§17–21 contain the earlier byte/review record.
+
+Landed c3a now owns the needed key on
+`WalkClassifiedBatch.LocalSortCenter`/`SortDistanceSq` and on the prepared
+particle record before the two FIFO lists see it. A separate classic grouped
+dispatcher sidecar survives only as dead storage and diagnostic hash input:
+`CachedBatch.LocalSortCenter`, `InstanceGroup.LocalSortCenters`, and their
+append/cache plumbing. Two additional tombstones pass a camera position into
+`DeferTransparentGroups` and `BuildTransparentSubmissionDigest`, then discard
+it. None feeds a draw, route, list choice, queue record, flush, or barrier.
+
+### 22.2 D1 — remove the dead grouped sort-center sidecar
+
+Delete `CachedBatch.LocalSortCenter` and
+`InstanceGroup.LocalSortCenters`, including constructor arguments, cache-hit
+delegate/plumbing, append parameters, per-frame clear/release calls, and the
+unused field in `AddSubmissionInstance`'s diagnostic digest. The resulting
+classic grouped path retains matrices, exact submission ordinal, clip slot,
+lights, indoor/detail/opacity/selection state, and every material key.
+
+This deletion must not touch these live retail keys:
+
+- `ObjectRenderData.SortCenter`;
+- `WalkClassifiedBatch.LocalSortCenter` and `SortDistanceSq`;
+- `WalkStaticStreamPopulator`'s transformed authored-center calculation and
+  stable descending per-cell insertion sort;
+- `ParticleRenderer`'s authored GfxObj sort center, prepared distance, and
+  object/particle merge;
+- building-degrade `ViewerDistanceTo`, opaque `InstanceGroup.SortDistance`,
+  portal-flood distance, private-viewport sorting, or off-screen particle
+  ordering.
+
+The `CurrentRenderDispatcherSubmission` digest deliberately stops hashing the
+deleted non-rendered sidecar. That is diagnostic cleanup, not a world-render
+change; submission order and every rendered field remain hashed.
+
+### 22.3 D2 — remove the dead alpha camera-parameter chain
+
+Remove `cameraWorldPosition` from
+`DeferTransparentGroups`, `BuildTransparentSubmissionDigest`,
+`CreateDispatcherSubmission`, `ObserveCurrentDispatcherSubmission`, and
+`ObserveClassifiedDispatcherSubmission`, plus all callers/tests. No
+`_ = cameraWorldPosition` tombstone may remain.
+
+Keep the camera output from `BeginEntityDispatch`, the camera argument to
+`PartitionInstanceGroups`, `InstanceGroup.SortDistance`, and
+`CompareOpaqueSubmissionOrder`: that is the still-live opaque/private grouped
+path and is outside the alpha deletion.
+
+### 22.4 D3 — truth cleanup and explicit non-changes
+
+The six `AlphaFlushCounts_*` rows remain evaluated KnownFailures. Their exact
+three reasons are: (1) the replay world is content-empty; (2) AP-238 coalesces
+EnvCell work to one `(cell,list)` token; (3) AP-239/AP-240 alter list
+membership for the named ordinary-Wb cases. Remove any surviving broad
+“per instance versus per subset” explanation; ordinary Wb and particle paths
+otherwise append per real subset. The live `AlphaFlushSites_*` rows remain.
+
+Static deletion verification must find no executable `RetailAlphaOrdering`,
+`FlushFartherThan`, alpha-submit `viewerDistance`, portal punch depth bias,
+`#129` eye-span cap, or stencil-mark pass. Do not delete generic RHI stencil
+support, change `PortalDepthMaskRenderer`, touch shaders/SPIR-V, or change
+AD-119/AP-238/AP-239/AP-240/AP-241/AP-242/AP-243. The historical mutation
+comments that quote the deleted old API may remain when clearly past tense.
+
+### 22.5 Required tests and mutation evidence
+
+Extend the existing production-facing tests, not a surrogate implementation:
+
+1. reflection/source shape proves `CachedBatch` and `InstanceGroup` have no
+   `LocalSortCenter(s)` sidecar while `WalkClassifiedBatch` still has
+   `LocalSortCenter` and `SortDistanceSq`;
+2. reflection/source shape proves the five D2 methods have no dead camera
+   parameter and neither tombstone remains, while `PartitionInstanceGroups`
+   still accepts and uses its camera position for opaque `SortDistance`;
+3. existing cache-hit composition, transparent submission-order digest,
+   group-clear, per-cell object order, particle merge, queue, allocation, and
+   shader/state pins remain green;
+4. a source-truth pin keeps the three `AlphaFlushCounts_*` reasons and rejects
+   the false broad explanation;
+5. a deletion pin rejects any production resurrection of
+   `RetailAlphaOrdering`, `FlushFartherThan`, or an alpha-submit
+   `viewerDistance`, without rejecting unrelated building/opaque/portal
+   distance owners.
+
+Every new pin gets a real sabotage. At minimum, record the actual first
+failure after independently restoring: (a) `InstanceGroup.LocalSortCenters`;
+(b) `CachedBatch.LocalSortCenter`; (c) the discarded camera parameter/tombstone
+on `DeferTransparentGroups`; (d) the discarded camera parameter on the
+transparent digest; (e) the false broad count explanation; and (f) one deleted
+alpha-order symbol. Restore each mutation exactly before the clean return.
+
+### 22.6 Scope, gates, and review
+
+Allowed production files:
+`src/AcDream.App/Rendering/Wb/CachedBatch.cs`,
+`WbDrawDispatcher.cs`, and comment-only cleanup in
+`WbDrawDispatcher.WalkClassify.cs`. Tests may change only
+`tests/AcDream.App.Tests/Rendering/Wb/InstanceGroupClearTests.cs`,
+`tests/AcDream.App.Tests/Rendering/Walk/WalkStaticStreamPopulatorTests.cs`, and
+the directly affected existing rendering test file if compile fallout requires
+it. Documentation is limited to this packet,
+`docs/architecture/worldbuilder-inventory.md`, and
+`docs/architecture/acdream-architecture.md`. No register edit is expected; if
+source truth disproves that, stop and return the fact instead of silently
+changing scope.
+
+Must not change queue/router/pipeline/list membership, capacity, flush/barrier,
+particle preparation, per-cell sort/merge, package/content/RHI/shader state,
+or graphical behavior. No client launch from the implementation/review
+worktree.
+
+Automated return: `git diff --check`; Release solution 0W/0E; focused Wb
+group/cache/digest + walk per-cell/order + queue/particle/router suite; both
+real production 0-B pins; shader/manifest/SPIR-V 32/32; hermetic lane; and
+InstalledDat with exactly the documented global set plus the six retained
+`AlphaFlushCounts_*`, no new failure. The implementer commits one bounded
+change on a clean worktree and returns exact files, counts, and mutation-first-
+failure text.
+
+Sequential reviews: first, retail/deletion fidelity verifies the named decomp
+and paired bytes, that only pre-append per-cell CYpt survives, and that every
+live distance owner above was preserved. Second, production/gate honesty checks
+call reachability, diagnostic-digest consequences, cache/reset/storage
+lifecycle, allocation, allowed scope, every mutation claim, and all gate
+counts. A failed lens gets one bounded fix contract; a third fix round stops
+and is written up. Dual PASS lands c3b and unlocks G3.