Audio: robust rate estimation + color-coded log levels

Harden the guessed-stream sample-rate measurement that produced wrong rates
(e.g. 44100 read as ~46205). New rate_estimator.hpp measures over longer
~0.5 s windows, rejects any window that doesn't snap to a standard rate
(standard rates are >8% apart, so a quantization/burst error big enough to
miss one lands in no-man's-land, never on a wrong neighbour), and requires
consensus across windows before committing. If consensus isn't reached it
commits a low-confidence estimate (new AudioFormat_LowConfidence, shown red)
rather than spinning or publishing garbage. Pure logic, unit-tested with
adversarial cadences (rate_estimator_test) incl. the real 46205 bug value.

Add log severity levels: hook logw/loge set LogRecord.level; the host Log
window colors warnings amber and errors red. The low-confidence rate logs a
warning. Protocol -> v15 (new format states); also reserves AudioFormat_Override.

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

hook/src/debug_log.hpp

@@ -13,7 +13,10 @@ namespace coop::hook
 {
 
 // Append a printf-style line to the log ring (if attached) and the file (if on).
+// logf = info, logw = warning, loge = error; the host colours the Log window by level.
 void logf(const char* fmt, ...);
+void logw(const char* fmt, ...);
+void loge(const char* fmt, ...);
 
 // Attach/detach the host's shared log ring so lines stream to the Log window.
 void set_log_ring(coop::LogRing* ring);