Add diagnostic tracing and fix ot_analyze_shape O(N^4) wire matching

CLAUDE.md

@@ -40,6 +40,8 @@ On headless Linux the viewer test needs `xvfb-run ctest …`. CI on all three pl
 
 **Error reporting.** Functions return `NULL`/`false` and write a message to `thread_local std::string g_last_error`. Callers retrieve it via `occt_templot_last_error()`. All public-facing implementations should `try { … } catch (Standard_Failure& e) { g_last_error = …; return …; }` around OCCT calls — OCCT throws on bad input.
 
+**Diagnostic tracing.** Off by default. Enable via `OCCT_TEMPLOT_TRACE=1` env var or by calling `ot_set_trace(true)` from a host language. When on, `OT_TRACE(...)` lines from `occt_templot_*.cpp` flush to stderr immediately (so a hung call is still visible), and OCCT's own `Message::DefaultMessenger()` is wired to stderr so internal `ShapeFix` / `Sewing` / `BRepCheck` output surfaces too. Helper lives in `src/occt_templot_trace.{h,cpp}`. When adding a new long-running function, bracket the OCCT call with `OT_TRACE("ot_foo: phase X start")` / `OT_TRACE("ot_foo: phase X done")` so a stuck call is localisable from the log.
+
 **Memory ownership.** Anything returned from `ot_*` that isn't a primitive must be paired with a free function: `ot_shape_free`, `ot_mesh_free`, `ot_edge_mesh_free`, `ot_viewer_destroy`, `ot_camera_destroy`, `ot_drawer_destroy`. The `OTMeshData` / `OTEdgeMeshData` structs hold heap-allocated arrays — the corresponding free functions zero out the struct so double-free is safe.
 
 ## OCCT dependency

CMakeLists.txt

@@ -47,6 +47,7 @@ set(SOURCES
     src/occt_templot_mesh.cpp
     src/occt_templot_viewer.cpp
     src/occt_templot_render_data.cpp
+    src/occt_templot_trace.cpp
 )
 
 add_library(simpleOCCTVP SHARED ${SOURCES})

pascal/occt_templot.pas

@@ -139,6 +139,10 @@ procedure occt_templot_shutdown; cdecl; external OCCT_LIB;
 function  occt_templot_version: PAnsiChar; cdecl; external OCCT_LIB;
 function  occt_templot_last_error: PAnsiChar; cdecl; external OCCT_LIB;
 
+{ Diagnostic tracing — also gated by env var OCCT_TEMPLOT_TRACE=1 }
+procedure ot_set_trace(enable: Boolean); cdecl; external OCCT_LIB;
+function  ot_get_trace: Boolean; cdecl; external OCCT_LIB;
+
 { ================================================================
   Shape Handle
   ================================================================ }

src/occt_templot.h

@@ -47,6 +47,15 @@ OT_EXPORT const char* occt_templot_version(void);
 /** Return the last error message, or NULL if no error. Thread-local. */
 OT_EXPORT const char* occt_templot_last_error(void);
 
+/** Enable/disable diagnostic tracing to stderr at runtime.
+ *  Also activated by setting the OCCT_TEMPLOT_TRACE=1 environment variable
+ *  before the library loads. When on, ot_* function entry/exit lines and
+ *  OCCT's internal Messenger output are flushed to stderr. */
+OT_EXPORT void ot_set_trace(bool enable);
+
+/** Returns the current trace state. */
+OT_EXPORT bool ot_get_trace(void);
+
 /* ================================================================
  * Shape Handle (opaque)
  * ================================================================ */