style(terminal): tighten string-retention rationale

(cherry picked from commit 6c0388db40)

src/renderer/src/lib/flatten-retained-slice.ts

@@ -1,11 +1,4 @@
-/**
- * V8 backs `String.prototype.slice` with a SlicedString that points at the whole parent, so a
- * short tail of a large chunk keeps that whole chunk alive. Concatenating forces a ConsString
- * whose flattening allocates a fresh sequential string of just this length, dropping the parent.
- *
- * Use this whenever a slice outlives the value it was cut from — a queued remainder, or an
- * overlap-trimmed payload handed to a component that will hold it.
- */
+// V8 slices can retain their full parent; force a standalone copy for values that outlive it.
 export function flattenRetainedSlice(value: string): string {
   return value.length === 0 ? value : `${value} `.slice(0, -1)
 }

src/renderer/src/lib/pane-manager/pane-terminal-output-scheduler.ts

@@ -50,7 +50,7 @@ type WriteTerminalOutputOptions = {
 
 type QueueChunk = {
   data: string
-  // Why: `data` may be a V8 SlicedString pinning a much larger parent; this is what the queue really holds alive.
+  // Tracks the backing data still reachable through this queue slot.
   retainedChars: number
   foreground: boolean
   forceForegroundRefresh: boolean
@@ -634,9 +634,7 @@ function takeQueuedChunk(entry: QueueEntry, limit: number): QueuedWrite | null {
       data += chunk.data
       remaining -= chunk.data.length
       entry.queuedChars -= chunk.data.length
-      // Why: compaction only splices every 64 chunks, so without this a fully consumed chunk keeps
-      // its (possibly parent-pinning) string and callbacks alive while charging nothing. Nothing
-      // reads below chunkIndex, so the drained slot only has to stay type-shaped.
+      // Clear drained slots before the 64-chunk compaction can release them.
       entry.chunks[entry.chunkIndex] = {
         data: '',
         retainedChars: 0,
@@ -658,7 +656,7 @@ function takeQueuedChunk(entry: QueueEntry, limit: number): QueuedWrite | null {
 
     data += chunk.data.slice(0, remaining)
     const residual = chunk.data.slice(remaining)
-    // Why: the residual is a SlicedString still pinning `retainedChars`; copy it flat once it pins 2x its own length so a drained 2MB chunk stops holding 2MB to serve a 1KB tail. Halving keeps total copying linear in the original chunk.
+    // Geometric flattening bounds retained parents while keeping total copy work linear.
     const flatten = residual.length * 2 <= chunk.retainedChars
     entry.chunks[entry.chunkIndex] = {
       ...chunk,
@@ -738,10 +736,7 @@ function enqueueChunk(
     ackCredit?: () => void
   }
 ): void {
-  // Why copy at the boundary: producers hand us slices and concatenations that pin far more than
-  // they measure - restore-overlap trims and OSC status stripping both do - and the queue holds
-  // this string long after the parent is otherwise dead. Owning our copy is what makes
-  // retainedChars true, and it costs ~0.1ms per 512KB against a ~30MB/s sustained drain.
+  // Own queued data so producer slices cannot pin larger PTY or restore buffers.
   const owned = flattenRetainedSlice(data)
   entry.chunks.push({
     data: owned,