D291/D306: close Dam intro truck glitch as faithful; add repro probes

D291 (user-captured) is D306: Dam intro camera 5, truck over the walkway
camera; reproduces at FovScale 100. All PC-specific leads refuted with
evidence: FOV, depth precision/DrawDistance, depth state (every truck
triangle is opaque z-tested), near-plane handling, wheel transforms. The
image is a depth-correct view of the authored model from under the truck.
GE_ZF's earlier "real fighting" was a +-255 z quantisation artefact.

TEMP tools: GE_INTROCAM=<n> pins the level intro's first camera
(bondview_r.c, #ifdef PORT, PRNG draw still consumed); GE_D306C depth-state
census in gfx_pc.cpp. Golden gate 3/3.

port/fast3d/gfx_pc.cpp

@@ -2637,6 +2637,40 @@ static void gfx_sp_tri1(uint8_t vtx1_idx, uint8_t vtx2_idx, uint8_t vtx3_idx, bo
     d75d_note_emit(videoGetFrameCount(), v_arr); // survived all rejection gates -> reaches GL
     d303_note_emit(videoGetFrameCount(), v_arr); // TEMP D303
     zf_note_emit(videoGetFrameCount(), v_arr);   // TEMP D306/D308
+    /* TEMP D306 (M-201): depth-state census of emitted triangles in a frame
+     * window, GE_D306C="f0 f1". One line per tri: depth flags as sent to GL,
+     * geometry_mode, other_mode_l, tile-0 texture, NDC centroid, z/w range and
+     * min w (<=0 = crosses the eye plane). Cap 60000. */
+    {
+        static int d306c = -1; static uint32_t d306f0 = 0, d306f1 = 0, d306n = 0; static float d306wmax = 1e30f;
+        if (d306c < 0) {
+            const char* e = getenv("GE_D306C");
+            d306c = (e && sscanf(e, "%u %u %f", &d306f0, &d306f1, &d306wmax) >= 2) ? 1 : 0;
+        }
+        const uint32_t fc = videoGetFrameCount();
+        if (d306c && fc >= d306f0 && fc <= d306f1 && d306n < 60000) {
+            float cx = 0, cy = 0, zmin = 1e9f, zmax = -1e9f, wmin = 1e9f;
+            for (int i = 0; i < 3; i++) {
+                const float w = v_arr[i]->w;
+                if (w < wmin) wmin = w;
+                if (w > 0.f) {
+                    const float zn = v_arr[i]->z / w;
+                    cx += v_arr[i]->x / w; cy += v_arr[i]->y / w;
+                    if (zn < zmin) zmin = zn;
+                    if (zn > zmax) zmax = zn;
+                }
+            }
+            cx /= 3.f; cy /= 3.f;
+            if (wmin > d306wmax) goto d306c_skip; /* optional 3rd arg: near geometry only */
+            {
+            const void* t0 = rendering_state.textures[0] ? (const void*)rendering_state.textures[0]->first.texture_addr : nullptr;
+            d306n++;
+            fprintf(stderr, "D306C f=%u dm=%02x geom=%08x oml=%08x tex0=%p c=(%.3f,%.3f) z=[%.5f,%.5f] wmin=%.2f\n",
+                    fc, rendering_state.depth_mode, rsp.geometry_mode, rdp.other_mode_l, t0, cx, cy, zmin, zmax, wmin);
+            }
+        }
+        d306c_skip:;
+    }
     d75d_note_emit_z(videoGetFrameCount(), v_arr, (used_textures[0] || used_textures[1]) ? 1 : 0, comb->used_textures[0] ? 1 : 0);
     for (int i = 0; i < 3; i++) {
         float z = v_arr[i]->z, w = v_arr[i]->w;