docs(physics): Phase L.2 movement collision conformance plan

Formalize Phase L.2 as the active holistic movement/collision program, align the roadmap and architecture docs, file tactical physics follow-ups, and refresh collision memory away from rewrite-from-zero guidance.

Co-authored-by: OpenAI Codex <codex@openai.com>

docs/ISSUES.md

@@ -177,6 +177,141 @@ missing is the plugin-API surface.
 
 ---
 
+## #30 — AutonomousPosition contact byte is too often grounded
+
+**Status:** OPEN
+**Severity:** HIGH
+**Filed:** 2026-04-29
+**Component:** physics / net / movement
+
+**Description:** Outbound movement can claim grounded contact even when the
+local resolver result is uncertain or airborne. `AutonomousPosition.Build`
+defaults `lastContact` to 1, and the app path needs an audit to ensure
+`ResolveResult.IsOnGround` is what reaches the wire.
+
+**Root cause / status:** Tracked under Phase L.2b. This can make ACE accept
+movement that is not actually retail-valid and can hide edge/step-down bugs.
+
+**Files:** `src/AcDream.Core.Net/Messages/AutonomousPosition.cs`,
+`src/AcDream.Core.Net/Messages/MoveToState.cs`,
+`src/AcDream.App/Input/PlayerMovementController.cs`.
+
+**Research:** `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+**Acceptance:** Ground contact byte is derived from the current resolved
+movement result for both autonomous heartbeat and movement-state sends. Tests
+cover grounded, airborne, and failed-transition cases.
+
+---
+
+## #31 — Low outdoor cell id can go stale after transition movement
+
+**Status:** OPEN
+**Severity:** HIGH
+**Filed:** 2026-04-29
+**Component:** physics / cells / movement
+
+**Description:** Local movement can cross 24m outdoor cell boundaries while
+the low cell id used for outbound full cell id remains stale. This can combine
+correct landblock high bits with the wrong outdoor-cell low byte.
+
+**Root cause / status:** Tracked under Phase L.2e. `CELLARRAY`,
+`CObjCell::find_cell_list`, adjacent-cell checks, and low-cell ownership are
+not fully ported.
+
+**Files:** `src/AcDream.Core/Physics/PhysicsEngine.cs`,
+`src/AcDream.Core/Physics/TransitionTypes.cs`,
+`src/AcDream.App/Input/PlayerMovementController.cs`.
+
+**Research:** `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+**Acceptance:** Crossing a 24m outdoor-cell seam updates the local resolved
+cell id and the outbound full cell id. Tests cover intra-landblock seams and
+landblock-edge seams.
+
+---
+
+## #32 — Retail edge-slide / cliff-slide / precipice-slide incomplete
+
+**Status:** OPEN
+**Severity:** HIGH
+**Filed:** 2026-04-29
+**Component:** physics / collision
+
+**Description:** When walking along walls, roof edges, cliff edges, or failed
+step-down boundaries, retail often slides along the boundary. acdream still
+hard-blocks or accepts too much in several of these cases.
+
+**Root cause / status:** Tracked under Phase L.2c. Named retail anchors include
+`CTransition::edge_slide`, `CTransition::cliff_slide`,
+`SPHEREPATH::precipice_slide`, and `SPHEREPATH::step_up_slide`.
+
+**Files:** `src/AcDream.Core/Physics/TransitionTypes.cs`,
+`src/AcDream.Core/Physics/BSPQuery.cs`,
+`tests/AcDream.Core.Tests/`.
+
+**Research:** `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+**Acceptance:** Synthetic and real-DAT tests cover wall-slide, roof-edge slide,
+cliff/precipice slide, failed step-up/step-down, and the jump-clears-edge case.
+
+---
+
+## #33 — Live entity collision shape collapses to one cylinder
+
+**Status:** OPEN
+**Severity:** MEDIUM
+**Filed:** 2026-04-29
+**Component:** physics / entities
+
+**Description:** Live world entities do not yet use exact retail
+`CSphere` / `CCylSphere` shape semantics. Several paths collapse the entity to
+a simplified root-centered cylinder or fallback radius, which is not enough for
+retail object and creature collision parity.
+
+**Root cause / status:** Tracked under Phase L.2d. Requires auditing object
+shape extraction, `Setup.Radius` fallback, building object identity, and live
+entity broadphase records against named retail.
+
+**Files:** `src/AcDream.Core/Physics/CollisionPrimitives.cs`,
+`src/AcDream.Core/Physics/ShadowObjectRegistry.cs`,
+`src/AcDream.Core/Physics/PhysicsDataCache.cs`.
+
+**Research:** `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+**Acceptance:** Live object collision uses the appropriate retail sphere or
+cylsphere data where available. Tests prove at least one multi-shape object and
+one live creature case no longer use the single-cylinder fallback.
+
+---
+
+## #34 — Missing routine local/server correction diagnostic
+
+**Status:** OPEN
+**Severity:** MEDIUM
+**Filed:** 2026-04-29
+**Component:** physics / net / diagnostics
+
+**Description:** The client needs an opt-in diagnostic that logs local predicted
+position/contact/cell, outbound movement fields, server `UpdatePosition` echo,
+and correction delta. Current correction visibility is too focused on portal
+arrival and not enough on normal walking.
+
+**Root cause / status:** Tracked under Phase L.2a/L.2b. Without this probe,
+ACE's tolerance can hide local collision divergence.
+
+**Files:** `src/AcDream.Core.Net/WorldSession.cs`,
+`src/AcDream.App/Input/PlayerMovementController.cs`,
+`src/AcDream.App/Rendering/GameWindow.cs`.
+
+**Research:** `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+**Acceptance:** With the diagnostic enabled, a walking session logs local
+resolved placement, outbound cell/contact fields, server echo placement, and
+correction delta in a grep-friendly format.
+
+---
+
 
 ## #2 — Lightning visual mismatch (sky PES path disproved)