quality presets: source comments match the rules (Low/Ultra, unknown Medium, High manual)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/include/quality_tier.h

@@ -37,8 +37,9 @@ const char *psx_quality_name(int tier);
 int psx_quality_from_name(const char *name);
 
 /* The preset this host should start from, and one line saying why
- * ("AMD integrated GPU: Low"). Ultra unless the class cannot hold 60 Hz even
- * at the dynamic floor; unknown hardware gets Medium. */
+ * ("AMD integrated GPU: Low"). Recognised hardware: Low or Ultra. Unknown
+ * GPU: Medium. Never High (manual only). The caller maps the result onto the
+ * title's offered presets with psx_quality_pick_offered. */
 int psx_quality_classify(const PsxHostInfo *h, char *reason, size_t reason_cap);
 
 /* Nearest preset the title offers (bit i of offered_mask = tier i): the

runtime/src/quality_tier.c

@@ -1,8 +1,10 @@
 /* quality_tier.c -- graphics preset autodetection rules (quality_tier.h).
  *
- * Ultra is the default; a GPU class, a thread count or memory size steps a
- * machine down only where Ultra cannot hold 60 Hz even at its dynamic floor
- * (docs/QUALITY_PRESETS.md). */
+ * A static heuristic, no benchmark (docs/QUALITY_PRESETS.md): recognised
+ * hardware gets Low or Ultra; an unrecognised GPU gets Medium (or the nearest
+ * lower preset the title offers, psx_quality_pick_offered); High is never
+ * detected, only chosen by the player. Few CPU threads or little memory cap
+ * the result at Low. */
 #include "quality_tier.h"
 
 #include <ctype.h>