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/shell/capture/render_in_place.cpp

@@ -2,9 +2,6 @@
 //
 // Includes reaper_plugin_functions.h WITHOUT REAPERAPI_IMPLEMENT — main.cpp is the
 // one TU that defines the API pointers; here they are extern.
-//
-// Traffic is one-way: this borrows capture's render, and capture may never borrow
-// this placement back.
 
 #include "shell/capture/render_in_place.h"
 
@@ -121,7 +118,11 @@ void RunRenderTrackInPlace(ReaSamplerSession& session) {
 
     const int trackCount = CountTracks(proj);
     const int srcIndex   = indexOfTrack(proj, trackCount, source);
-    if (srcIndex < 0) { refuse("the source track is no longer in the project"); return; }
+    if (srcIndex < 0) {
+        refuse("the source track is no longer in the project; the render landed at " +
+               res.absolutePath + " but was not placed.");
+        return;
+    }
 
     const SiblingPlacement place =
         siblingPlacement(folderDepths(proj, trackCount), srcIndex);
@@ -137,8 +138,13 @@ void RunRenderTrackInPlace(ReaSamplerSession& session) {
     InsertTrackInProject(proj, place.insertIndex, /*flags=*/0);
     MediaTrack* fresh = GetTrack(proj, place.insertIndex);
     if (!fresh) {
-        Undo_EndBlock2(nullptr, "", 0);
-        refuse("could not create the result track");
+        // InsertTrackInProject already mutated the project by this point, so the
+        // "no ext-state write -> discard" idiom does not apply here — a discard would
+        // leave the orphaned track un-undoable.
+        Undo_EndBlock2(nullptr, "ReaSampler: render in place (failed to create result track)",
+                       -1);
+        refuse("could not create the result track; the render landed at " +
+               res.absolutePath + " but was not placed.");
         return;
     }
 
@@ -151,7 +157,6 @@ void RunRenderTrackInPlace(ReaSamplerSession& session) {
     }
     SetMediaTrackInfo_Value(fresh, "I_FOLDERDEPTH",
                             static_cast<double>(place.newDepth));
-    TrackList_AdjustWindows(false);
 
     // GetTrackColor returns the colour already OR'd with 0x1000000 and 0 for "no
     // colour set", which I_CUSTOMCOLOR reads as unused — so one line clones a colour
@@ -161,6 +166,9 @@ void RunRenderTrackInPlace(ReaSamplerSession& session) {
     const std::string freshName = captureTrackName(trackName(source));
     setTrackName(fresh, freshName);
 
+    // After every attribute write, per the SDK header's manual-panel-update caveat.
+    TrackList_AdjustWindows(false);
+
     // Unsnapped and unrounded, deliberately: this placement IS the null test performed
     // automatically, so snapping it to the grid would move the audio off the position
     // it was rendered from. InsertOptions{} defaults give native length and no conform.