fix(physics): traverse prepared indoor portal topology

docs/ISSUES.md

@@ -103,6 +103,33 @@ Copy this block when adding a new issue:
 
 ---
 
+## #246 — Prepared indoor cells stopped traversing their portals
+
+**Status:** DONE — 2026-07-26; connected house/dungeon gate passed
+**Severity:** HIGH
+**Filed:** 2026-07-26
+**Component:** physics / cell membership / portal visibility
+
+**Description:** Houses and dungeons could collide with empty space, expose
+the background through walls, retain the wrong room, and fail on stairs after
+the parsed collision graph was removed.
+
+**Root cause / status:** The prepared package retained exact portal topology,
+planes, and BSPs, but `CellTransit.FindTransitCellsSphere` still returned
+immediately when the old parsed portal-polygon dictionary was absent. It now
+consumes the prepared topology's direct polygon index, preserving retail's
+portal traversal and failing loudly on corrupt topology. Synthetic graph-free
+tests and the exact connected Holtburg cottage camera path pass, along with
+1,778 physics tests / 1 skip.
+
+**Research:**
+[`research/2026-07-26-prepared-indoor-transit-regression.md`](research/2026-07-26-prepared-indoor-transit-regression.md).
+
+**Acceptance:** PASSED — the user confirmed house/dungeon collision, doorway
+entry, stairs, and interior rendering work in the corrected connected build.
+
+---
+
 ## #245 — Distant Use stayed busy without turning or walking
 
 **Status:** DONE — 2026-07-25; connected gate passed

docs/architecture/worldbuilder-inventory.md

@@ -168,6 +168,16 @@ This remains one `DatCollection`, one preparation algorithm, and one package
 mmap. Evidence:
 `docs/research/2026-07-25-slice-i7-closeout.md`.
 
+**Prepared indoor-transit consumer correction (2026-07-26).** The package
+already retained exact portal planes through
+`FlatEnvCellTopology.PolygonIndex` plus the aliased CellStruct portal-polygon
+table. The production `CellTransit` consumer now reads that prepared
+relationship directly; it no longer treats the intentionally absent parsed
+`CellPhysics.PortalPolygons` dictionary as “this cell has no portals.” No
+package schema, bake, DAT reader, collision formula, or render portal graph
+changed. Evidence:
+`docs/research/2026-07-26-prepared-indoor-transit-regression.md`.
+
 **Retail VFX hook compatibility seam (2026-07-14).** Chorizite.DatReaderWriter
 2.1.7 models `CreateBlockingParticleHook` as the common hook header only, while
 retail inherits the complete `CreateParticleHook` payload. The narrow readers in

docs/plans/2026-07-25-modern-runtime-slice-i.md

@@ -343,6 +343,15 @@ GPU/frame-time and ordinary-process memory comparison remains a physical-
 display measurement, not a Slice-I correctness blocker. Evidence:
 [`../research/2026-07-25-slice-i7-closeout.md`](../research/2026-07-25-slice-i7-closeout.md).
 
+**Corrective gate 2026-07-26.** Later connected house/dungeon testing exposed
+one I7 consumer omission: `CEnvCell::find_transit_cells` still required the
+deleted parsed portal-polygon dictionary, even though the prepared topology
+and polygon table retained the exact same plane. The production consumer now
+uses that direct prepared index. Synthetic graph-free tests and the captured
+Holtburg cottage camera path prove identical graph/prepared results; no
+package rebake or parsed-graph restoration is needed. Evidence:
+[`../research/2026-07-26-prepared-indoor-transit-regression.md`](../research/2026-07-26-prepared-indoor-transit-regression.md).
+
 ## 4. Commit order
 
 Each unit is independently buildable and reversible:

docs/research/2026-07-26-prepared-indoor-transit-regression.md

@@ -0,0 +1,90 @@
+# Prepared indoor transit regression
+
+**Date:** 2026-07-26
+**Scope:** Slice-I prepared collision consumer correction
+**Behavioral boundary:** No collision formula, portal rule, or renderer
+behavior changed. This restores the existing retail traversal over the
+production flat representation.
+
+## Symptom and connected evidence
+
+After the Slice-I parsed-graph removal, entering houses or dungeons could:
+
+- collide with empty space at a doorway or room boundary;
+- retain the wrong indoor cell on stairs or upper floors;
+- expose the world background through the interior portal view.
+
+The connected capture at
+`.test-out/indoor-visibility-20260726-220007/stdout.log` placed the player in
+Holtburg cottage vestibule `0xA9B40150`, with the chase-camera eye outside the
+doorway in outdoor landcell `0xA9B40029`. The original DAT graph advanced the
+camera transition from `0xA9B40150` to `0xA9B40029`. The prepared production
+path retained `0xA9B40150`, causing collision and portal rendering to share
+the same wrong viewer-cell root.
+
+## Retail oracle
+
+Named retail:
+
+- `CEnvCell::find_transit_cells @ 0x0052C820`
+- `CObjCell::find_cell_list`
+- `CEnvCell::find_visible_child_cell`
+
+Consolidated pseudocode:
+[`acclient_indoor_transitions_pseudocode.md`](acclient_indoor_transitions_pseudocode.md).
+
+For each `CCellPortal`, retail reads that portal's polygon plane from the
+owning `CCellStruct`. An exterior portal admits outdoor cells when any path
+sphere straddles the plane. An interior portal tests the loaded neighbor's
+cell-containment BSP, using the plane only as an unloaded-cell hint.
+
+## Root cause
+
+The prepared package was complete:
+
+- `FlatEnvCellTopology.Portals[i].PolygonIndex` retained the direct portal
+  polygon index;
+- `FlatCellStructureCollisionAsset.PortalPolygons` retained the exact plane;
+- prepared containment and physics BSPs matched the original DAT graph.
+
+`CellTransit.FindTransitCellsSphere`, however, still began with:
+
+```text
+if currentCell.PortalPolygons is null: return
+```
+
+`PortalPolygons` is the old parsed-DAT dictionary and is intentionally null in
+production after Slice I7. Therefore every prepared indoor cell skipped its
+entire portal loop. The I4/I5 differential referee covered BSP queries and
+complete resolver results, but did not exercise portal-plane lookup after the
+parsed graph had been removed, allowing the representation-boundary defect to
+escape.
+
+## Correction
+
+`CellTransit` now resolves the exact same portal plane from:
+
+1. the parsed dictionary in explicit graph-oracle fixtures; or
+2. the prepared topology's direct polygon index and flat polygon table in
+   production.
+
+Prepared topology/list mismatches and invalid polygon indices fail loudly as
+corrupt publication rather than silently disabling indoor traversal. Portal
+iteration order, comparisons, sphere transforms, neighbor containment, and
+outside admission remain unchanged.
+
+## Automated evidence
+
+- Synthetic prepared exterior-portal test with no parsed polygon dictionary.
+- Synthetic prepared loaded-neighbor test with no parsed containment tree.
+- Exact connected Holtburg cottage camera path:
+  graph and prepared paths both end in `0xA9B40029` at identical position.
+- Installed-DAT graph/flat coverage expanded across the Holtburg cottage and
+  inn vestibules, connectors, stairwell, upper floor, and inn shell.
+- Physics-focused Release tests: 1,778 passed / 1 skipped.
+- Interaction/projection focused App tests: 127 passed.
+- Client-object ordering tests: 82 passed.
+- Complete Release build: passed with zero warnings.
+
+No divergence-register row is required: the correction removes an accidental
+production divergence and introduces no replacement behavior.