probe(physics): ACDREAM_PROBE_SUPPORT + ACDREAM_WIRE_MESH — separate #337's three candidates

The user is wedged at the top of Neftet rock plateaus, jumps sink into the
mesh, and a corpse falls straight through. ACDREAM_PROBE_REACH already ruled
out its own domain: blocked=0, every candidate tested-ok. Three candidates
remain — terrain support, a collision mesh not where its visual is, or the
transition wedging on an unobstructed path.

ACDREAM_PROBE_RESOLVE alone cannot separate them. It prints a three-value
contact-plane token, no plane normal, no plane height, no terrain sample and
no plane provenance, so all three produce the same line. Two additions:

[support] — one line per resolve for EVERY body, not just the player. A corpse
is a plain physics body with no player-specific logic, so its fall-through is
the cheapest available control on "movement code vs geometry data", and it is
invisible to any player-filtered probe. The line samples the outdoor terrain
INDEPENDENTLY at the body's own out-XY and prints the contact plane's own
height at that same XY. Two heights at one point make support=terrain /
object / none a measurement rather than an inference, and cpSrc= names the
site that asserted the plane so provenance and classification cross-check.

[geom] — once per GfxObj that comes near a mover: the object's physics-BSP
vertex cloud against its visual mesh AABB in the same local frame, through the
same prepared accessors the resolver queries. verdict=coincident REFUTES the
working hypothesis for that object outright; no-physics-bsp / empty-physics-bsp
/ displaced / extent-mismatch each name a specific data defect. Built to
refute, not to confirm — two diagnoses on this defect's lineage have already
been refuted by measurement.

ACDREAM_WIRE_MESH upgrades the existing F2 overlay, which drew a broadphase
proxy cylinder for BSP objects and so could not answer the question at all, to
the real physics-BSP polygon edges (cyan) beside the visual mesh box (magenta)
and the terrain surface (yellow). Own class per code-structure rule 1.

The provenance latch lives on PhysicsDiagnostics, not on CollisionInfo. Two
fields there first — the obvious home — broke the flat/graph differential
referee and the scratch-reset poison test, both of which compare CollisionInfo
member-for-member. Teaching either to skip a member is a one-line green fix
that puts a permanent hole in a referee whose whole job is comparing
everything. Captured as feedback_probe_state_off_compared_types.

Seven tests cover the support classifier's boundaries: a wrong classifier does
not fail to answer, it answers confidently wrong.

Gates: Release build 0 errors; complete suite 11,225 passed / 4 skipped / 0
failed from a cleaned tree — baseline 11,218/4/0 plus exactly the seven new
tests, skips unchanged.

Issue #337 filed with the symptom set, what is ruled out, and a table of what
each possible output means. All of this is TEMPORARY and recorded for
stripping with the physics-probe family.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/AcDream.Core/Rendering/RenderingDiagnostics.cs

@@ -783,4 +783,52 @@ public static class RenderingDiagnostics
     /// </summary>
     public static string? FrameHistoryPath { get; } =
         Environment.GetEnvironmentVariable("ACDREAM_FRAME_HISTORY");
+
+    // ── #337 collision-mesh wireframe (2026-08-06 — TEMPORARY) ──────────────
+    //
+    // The F2 collision overlay already existed, but for a BSP object it drew a
+    // proxy cylinder sized from the REGISTERED BROADPHASE RADIUS. That shows
+    // where the collision system thinks the object roughly is; it cannot show
+    // where the collision SURFACES are, which is the only thing that answers
+    // "is the collision geometry where the visual geometry is". The knobs
+    // below turn F2 into the real answer: the actual physics-BSP polygon
+    // edges, in world space, next to the same object's visual mesh box.
+    //
+    // Off by default, so F2 keeps its old cheap behaviour for anyone who wants
+    // it and this costs nothing until asked for.
+
+    /// <summary>
+    /// When true, the F2 collision overlay draws each nearby object's REAL
+    /// physics-BSP polygon edges (cyan) and, beside them, the same object's
+    /// visual mesh bounding box (magenta), plus the terrain triangle under the
+    /// player (yellow). Any separation between the cyan surfaces and the
+    /// object you can see is the "collision is not where the visual is"
+    /// defect, read directly off the screen instead of inferred from a log.
+    /// Initial state from <c>ACDREAM_WIRE_MESH=1</c>.
+    /// TEMPORARY — strip with the #337 probe family.
+    /// </summary>
+    public static bool CollisionMeshWireframeEnabled { get; set; } =
+        Environment.GetEnvironmentVariable("ACDREAM_WIRE_MESH") == "1";
+
+    /// <summary>
+    /// Radius in metres around the player within which
+    /// <see cref="CollisionMeshWireframeEnabled"/> resolves polygon geometry.
+    /// A whole landblock of rock is far more geometry than a line list wants;
+    /// 30 m covers everything you can wedge against. Override with
+    /// <c>ACDREAM_WIRE_RADIUS=&lt;metres&gt;</c>.
+    /// </summary>
+    public static float CollisionMeshWireframeRadius { get; set; } =
+        ParsePositiveFloat(
+            Environment.GetEnvironmentVariable("ACDREAM_WIRE_RADIUS"),
+            fallback: 30f);
+
+    private static float ParsePositiveFloat(string? raw, float fallback)
+        => float.TryParse(
+               raw,
+               System.Globalization.NumberStyles.Float,
+               System.Globalization.CultureInfo.InvariantCulture,
+               out float value)
+           && value > 0f
+               ? value
+               : fallback;
 }