Loop-crossfade-ux review fixes: parked-drag no longer fakes LOOP OFF, waveform label contrast fixed, hover memoizes its bank read

Also corrects the cap-area, em-dash, glyph-overhang and heuristic-comment findings noted in review.

src/shell/instrument/reasampler_editor.h

@@ -337,9 +337,10 @@ private:
     // instance's own SampleRefs as the self-contained fallback. "" when unresolvable.
     std::string samplePathFor(const std::string& sampleId) const;
 
-    // The effective loop + start markers for the loaded capture. The state machine behind them
-    // — which stored source wins, when the pair re-parks, what the two OFF states mean — is the
-    // pure loop_marks module's; this only reads the bank intrinsic it cannot see.
+    // The effective loop + start markers for the loaded capture; the state machine behind them
+    // is the pure loop_marks module's. With no override set this costs a bridge read plus a bank
+    // parse — hoverWaveform calls it on every WM_MOUSEMOVE, so the answer is memoized (see
+    // HoldNeedKey below, which this shares) rather than paid per move.
     SetupMarkers pickedMarkers(std::int64_t frames) const;
 
     // Whether the loop controls answer at all: the sustain loop is Gate-only, so in Trigger the
@@ -365,16 +366,22 @@ private:
     bool resolveBakeHoldNeeded();
 
     // What that answer was last computed against. Invalidated wholesale by refreshFromBank,
-    // which is where the bank half of the input changes.
+    // which is where the bank half of the input changes. pickedMarkers' own memo (below) shares
+    // this key shape rather than declaring a second one; resolveBakeHoldNeeded leaves startPoint
+    // at its default (nullopt) since its own answer doesn't depend on it.
     struct HoldNeedKey {
         std::string sampleId;
         std::optional<SampleLoop> loopOverride;
         std::int64_t crossfade = 0;
+        std::optional<std::int64_t> startPoint;
         bool operator==(const HoldNeedKey& other) const;
     };
     HoldNeedKey holdNeedKey_;
     bool holdNeedValid_ = false;
     bool holdNeedAnswer_ = false;
+    mutable HoldNeedKey marksKey_;
+    mutable SetupMarkers marksCache_;
+    mutable bool marksValid_ = false;
 
     // Writes `m` into params_ as the loop/start override. Does NOT call commitAndReload —
     // callers decide live-drag vs final commit.