New static `AcDream.Core.Physics.PhysicsDiagnostics` holds two
runtime-toggleable flags initialized from env vars:
- ACDREAM_PROBE_RESOLVE=1 — emit one [resolve] line per
PhysicsEngine.ResolveWithTransition call: input/target/output
position+cell, ok-vs-partial, grounded-in, contact-plane status,
wall normal if hit, walkable-polygon valid, moving entity id.
- ACDREAM_PROBE_CELL=1 — emit one [cell-transit] line per
PlayerMovementController.CellId change: old → new cell, current
world position, reason tag (resolver / teleport).
Both also exposed as runtime-toggleable checkboxes in the DebugPanel
"Diagnostics" section. Unlike the existing four Dump-* checkboxes
(which only mirror sticky-at-startup env vars), the two new ones
forward directly to PhysicsDiagnostics — toggling on/off takes
effect on the next physics resolve, no relaunch.
Why now: L.2's plan-of-record (docs/plans/2026-04-29-movement-collision-
conformance.md) explicitly says "Land L.2a diagnostics first. Do not
make another physics change blind." This slice closes the most-load-
bearing gap in L.2a — a general-purpose probe on the resolver outcome
and a cell-transit log — so that later L.2b/c/d/e physics changes can
be evidence-driven instead of guessed. Foundation for the indoor /
dungeon walking trajectory (G.3 unblock).
Pure additive: when both flags are off (default), the probes collapse
to a single static-bool read per resolve, zero log cost. PlayerMovement
Controller's two CellId-mutation sites are now routed through a
private UpdateCellId(reason) helper for diag chokepoint.
Build green, 1032/1040 unit tests pass. The 8 failing tests are
pre-existing on the branch base (verified by stash-and-rerun);
none touch resolver or cell-transit code; all fail identically with
this slice stashed. Investigation deferred to a follow-up.
Refs: docs/plans/2026-04-29-movement-collision-conformance.md (L.2a
shipped-slice note added in same commit).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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