Remediate Phase P render-in-place review findings

Fix the ProjectMedia refusal path's false bank claims and file relocation, an unreachable-undo idiom, and eight comment/doc accuracy issues.

src/core/capture/capture_name.cpp

@@ -90,8 +90,10 @@ std::string captureTrackName(const std::string& sourceName) {
     const std::string prefix(kCaptureTrackPrefix);
     // A source with no readable name yields the bare word rather than a trailing
     // space; both spellings are fixed points, which is what makes the whole function
-    // one (a track named exactly "Capture" must not become "Capture Capture").
-    const std::string bare = prefix.substr(0, prefix.size() - 1);
+    // one (a track named exactly "Capture" must not become "Capture Capture"). Read
+    // from kCaptureTrackPrefixBare rather than chopped off prefix, so the two names
+    // can't drift out of sync with each other (both expand from the same header token).
+    const std::string bare = kCaptureTrackPrefixBare;
 
     if (sourceName.empty()) return bare;
     if (sourceName == bare) return sourceName;

src/core/capture/capture_name.h

@@ -59,10 +59,20 @@ std::string formatCaptureStamp(const CaptureStamp& stamp);
 
 CaptureName composeCaptureName(const CaptureNameInputs& in);
 
+// The single source of truth for the word itself — kCaptureTrackPrefixBare and
+// kCaptureTrackPrefix below both expand from this one token, so editing it can never
+// desync captureTrackName's "no readable source name" bare-word fallback from the
+// separator-terminated prefix it is derived from.
+#define REASAMPLER_CAPTURE_TRACK_WORD "Capture"
+
+// The bare word behind kCaptureTrackPrefix, needed by captureTrackName's
+// no-readable-source-name fallback.
+inline constexpr const char* kCaptureTrackPrefixBare = REASAMPLER_CAPTURE_TRACK_WORD;
+
 // Prefixed onto a source track's name to name the track a render-in-place created.
 // A display convention, not a persisted key — unlike a lane prefix or an action-id
 // suffix, changing it later strands nothing.
-inline constexpr const char* kCaptureTrackPrefix = "Capture ";
+inline constexpr const char* kCaptureTrackPrefix = REASAMPLER_CAPTURE_TRACK_WORD " ";
 
 // The new track's name for a render of `sourceName`. IDEMPOTENT — a fixed point on
 // its own output, so a second render over a result track yields "Capture MONEY"

src/core/capture/track_topology.h

@@ -43,8 +43,10 @@ struct SiblingPlacement {
 // Levels are absolute nesting depths recovered from the deltas (level[0] = 0,
 // level[i+1] = level[i] + depth[i]). A folder parent's insert point is the first
 // following track back at the source's own level — i.e. after the whole folder;
-// everything else inserts directly below the source. The two writes preserve the
-// total delta sum, so no track after the insertion changes level.
+// everything else inserts directly below the source. On a well-formed delta list
+// (one whose deltas sum to zero) the two writes preserve the total delta sum, so no
+// track after the insertion changes level — the malformed case below does not carry
+// that guarantee; the clamp keeps the result legal, not level-preserving.
 //
 // A malformed list (deltas not summing to zero, an out-of-range srcIndex) CLAMPS to
 // the nearest legal placement rather than asserting: the failure mode of a corrupt