feat(debug): geom_correction TCP command — is the correction engaging?

Both [video] enhancements are silent no-ops on anything they cannot prove is
projected geometry: a vertex whose sub-pixel fraction was never cached, or a
packet whose position words lack full GTE projection provenance, just draws the
faithful way. So the enable flag alone says nothing about whether a given title
benefits, and the existing hit counters had no reader.

geom_correction reports the flag plus the free-running geometry_vertex_hits and
perspective_triangles totals, so per-title bring-up can tell an engaged
correction from an inert one before anyone argues about screenshots. Sample
twice and diff for a per-window rate.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

TCP_COMMANDS.md

@@ -50,6 +50,7 @@ Columns: **N** = native, **D** = DuckStation oracle.
 | `read_scratch` |   | ✓ | `addr`, `len` | Read PS1 scratchpad (0x1F800000 region) |
 | `read_vram` / `vram_peek` | ✓¹ | ✓ | `x`, `y`, `w`, `h` | Read 16-bit VRAM pixels (max 128×128) |
 | `gpu_state` | ✓ | ✓ | — | Display area, display depth, draw offset, GPUSTAT, clip rect, xfer state |
+| `geom_correction` |   | ✓ | — | `[video] geometry_correction` / `perspective_texturing` engagement: enable flag plus free-running `geometry_vertex_hits` and `perspective_triangles` totals. Both enhancements silently fall back to the faithful path on anything they cannot prove is projected geometry, so a zero counter with the flag on means the title never qualifies — sample twice and diff for a rate |
 | `sio_state` | ✓ | ✓ | — | SIO registers + (native only) pad/memcard protocol + TX/RX history |
 | `irq_state` | ✓ | ✓ | — | `I_STAT`, `I_MASK` (both), plus chain state on native |
 | `dma_state` | ✓ | ✓ | — | DPCR, DICR, all 7 channel states (madr/bcr/chcr) |

runtime/src/debug_server.c

@@ -4874,6 +4874,28 @@ static void handle_write_ram(int id, const char *json)
     send_ok(id);
 }
 
+/* geom_correction — is [video] geometry_correction / perspective_texturing
+ * actually doing anything on THIS title?
+ *
+ * Both enhancements are silent no-ops on content they cannot prove is
+ * projected geometry: a vertex whose sub-pixel fraction was never cached, or a
+ * packet whose position words lack full GTE projection provenance, simply draws
+ * the faithful way. So "enabled" alone tells you nothing — these counters are
+ * how you tell an engaged correction from an inert one. Both are free-running
+ * totals; sample twice and diff for a per-window rate. */
+static void handle_geom_correction(int id, const char *json)
+{
+    (void)json;
+    send_fmt("{\"id\":%d,\"ok\":true,"
+             "\"geometry_correction\":%d,"
+             "\"geometry_vertex_hits\":%u,"
+             "\"perspective_triangles\":%u}",
+             id,
+             gte_geometry_correction_enabled(),
+             (unsigned)gte_geometry_correction_hits(),
+             (unsigned)gpu_texture_correction_hits());
+}
+
 static void handle_gpu_state(int id, const char *json)
 {
     (void)json;
@@ -12603,6 +12625,7 @@ static const CmdEntry s_commands[] = {
     { "dump_ram",          handle_read_ram },   /* alias: one request, one response */
     { "write_ram",         handle_write_ram },
     { "gpu_state",         handle_gpu_state },
+    { "geom_correction",   handle_geom_correction },
     { "ws_aspect_cone_site", handle_ws_aspect_cone_site },
     { "ws_margin",         handle_ws_margin },
     { "ws_hud_mode",       handle_ws_hud_mode },

tools/debug_client.py

@@ -220,6 +220,11 @@ def build_cmd(args):
         return {"cmd": "read_scratch", "addr": addr, "len": length}, pretty_json
     elif cmd == "gpu":
         return {"cmd": "gpu_state"}, pretty_json
+    elif cmd in ("geom", "geom_correction"):
+        # Are the [video] geometry_correction / perspective_texturing
+        # enhancements actually engaging on this title? Free-running totals;
+        # sample twice and diff for a per-window rate.
+        return {"cmd": "geom_correction"}, pretty_json
     elif cmd == "overlay":
         return {"cmd": "overlay_state"}, pretty_json
     elif cmd == "watch":