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>

memory/project_movement_collision_conformance.md

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+# Movement & Collision Conformance Crib
+
+## Phase
+
+Active phase: **L.2 - Movement & Collision Conformance**.
+
+Plan: `docs/plans/2026-04-29-movement-collision-conformance.md`.
+
+Roadmap: `docs/plans/2026-04-11-roadmap.md`.
+
+## One-Sentence Framing
+
+B.3 shipped the MVP resolver foundation; L.2 is the holistic conformance
+program for physics, collision, buildings, edge/wall sliding, cell ownership,
+movement packets, and server correction.
+
+## Active Movement Spine
+
+```text
+InputDispatcher / PlayerMovementController
+  -> MotionInterpreter + local body prediction
+  -> PhysicsEngine.ResolveWithTransition
+  -> TransitionTypes + BSPQuery + ShadowObjectRegistry
+  -> ResolveResult contact/cell state
+  -> MoveToState / AutonomousPosition outbound messages
+  -> WorldSession server echo or correction diagnostics
+```
+
+## Lane Ownership
+
+- L.2a: truth probes, diagnostics, fixture capture.
+- L.2b: movement wire/contact truth, cell id on packets, correction handling.
+- L.2c: transition parity, edge-slide, cliff-slide, precipice-slide,
+  `NegPolyHit`.
+- L.2d: `CSphere` / `CCylSphere`, live entity shapes, building object identity.
+- L.2e: outdoor seams, `CELLARRAY`, `find_cell_list`, adjacent-cell checks,
+  `cell_bsp`, building entry/exit boundaries.
+- L.2f: real-DAT fixtures and live retail-observer conformance.
+
+## Non-Negotiables
+
+- Grep named retail before changing AC-specific physics or movement behavior.
+- Do not treat ACE accepting a position as proof of retail collision parity.
+- Do not reintroduce rewrite-from-zero collision guidance. Continue the partial
+  retail port by L.2 lanes.
+- G.3 dungeon/portal delivery waits on L.2e for trustworthy cell/building
+  ownership.
+- L.1 animation work must coordinate with L.2 when root motion or observer
+  movement changes the predicted body path.