Fix ref-count underflow, PSP timezone units, thread restart race, color codegen

- util/ref.c: refUnlock's assert(count >= 0) on an unsigned count was
  tautological, so a double-unlock silently underflowed to UINT32_MAX
  instead of asserting. Now asserts count > 0 before decrementing.
- duskpsp/time/timepsp.c: timeGetRealTimeZonePSP returned hours while
  every other platform (and timeepoch.c's math) expects seconds.
- thread.c: threadHandler reset threadId outside the mutex, after
  signaling STOPPED, letting a caller's immediate threadStart() race
  threadStartRequest()'s "thread id not 0" assert. threadId is now
  reset inside the same locked section.
- tools/color.py: whole-number CSV channels (0, 1) produced invalid C
  float literals (0f, 1f) for the generated COLOR_*_3F/_4F macros.
  Route through float() so they always stringify with a decimal point.

Also adds .claude/code-check.md: a full review pass over every
subsystem in src/dusk/, with the above (plus several other findings
not yet acted on) written up in detail.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tools/color.py

@@ -48,6 +48,11 @@ out = [
 js = []
 for name, (r, g, b, a) in colors.items():
   r8, g8, b8, a8 = (int(float(ch) * 255) for ch in (r, g, b, a))
+  # Route through float() rather than the raw CSV string -- a whole-number
+  # channel like "0" or "1" has no decimal point, and "0f"/"1f" aren't
+  # valid C float literals (float() always stringifies with one, e.g.
+  # "0.0"/"1.0").
+  rf, gf, bf, af = (float(ch) for ch in (r, g, b, a))
   macro = "COLOR_" + name.upper()
   camel = "".join(p[0].upper() + p[1:].lower() for p in name.split("_"))
 
@@ -55,8 +60,8 @@ for name, (r, g, b, a) in colors.items():
     f"// {name}",
     f"#define {macro}_4B  color4b({r8}, {g8}, {b8}, {a8})",
     f"#define {macro}_3B  color3b({r8}, {g8}, {b8})",
-    f"#define {macro}_3F  color3f({r}f, {g}f, {b}f)",
-    f"#define {macro}_4F  color4f({r}f, {g}f, {b}f, {a}f)",
+    f"#define {macro}_3F  color3f({rf}f, {gf}f, {bf}f)",
+    f"#define {macro}_4F  color4f({rf}f, {gf}f, {bf}f, {af}f)",
     f"#define {macro}     {macro}_4B",
     "",
   ]