all: trim the history essays out of the longest comments

From the audit (#5179). Ten comment blocks narrated how the code got here:
milestone numbers, earlier values, the operator's verdict on an old design.
Each now says what the code does and why, and the history stays in git,
Scribe and docs/sync.md. The protocol-version comment in sync.py points at
docs/sync.md's policy section, which already lists every bump.

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

frontend/src/notes/blocks.ts

@@ -110,28 +110,18 @@ export function plusTask(blocks: EditorBlock[]): { blocks: EditorBlock[]; focus:
 }
 
 /**
- * Re-read ONE prose block for `- [ ] ` lines somebody typed by hand.
+ * Re-read ONE prose block for `- [ ] ` lines somebody typed by hand, so a marker
+ * typed in the editor becomes an item without closing and reopening the note.
  *
- * `splitBlocks` runs once, when the editor opens. After that the blocks are the state
- * and nothing reads the body again — every edit travels the other way, through
- * `joinBlocks`. So a marker typed by hand stayed literal text on screen until the note
- * was closed and reopened, even though it was already a real item in storage and the
- * card was already drawing a checkbox for it. The editor was the only place that
- * disagreed.
+ * On blur, and only the block being left: re-splitting on a keystroke would move the
+ * caret, and converting the moment `- [ ]` is complete would catch an item with no
+ * text yet.
  *
- * ON BLUR, and only the block being left. There is no good moment to convert while
- * someone is typing: re-splitting on a keystroke moves the caret out of the word being
- * written, and converting the instant `- [ ]` is complete does it before the item has
- * any text. Blur is the one moment the person has demonstrably finished with the block,
- * so a re-split costs no caret and cannot catch a half-typed line.
+ * Returns THE SAME ARRAY when there was nothing to promote; the caller relies on that
+ * to leave the ref alone, so a blur that changed nothing doesn't re-key every field.
  *
- * Returns THE SAME ARRAY, not an equal copy, when there was nothing to promote — the
- * caller leans on that to leave the ref alone, and a blur that changed nothing must not
- * re-key every field below it.
- *
- * Non-canonical markers (`- [X]`, an odd bullet) come back canonical, exactly as they
- * would have on reopen. That is the only case where this changes the body rather than
- * only the way it is drawn.
+ * Non-canonical markers (`- [X]`, an odd bullet) come back canonical, as they would on
+ * reopen.
  */
 export function promoteTasks(blocks: EditorBlock[], index: number): EditorBlock[] {
   const block = blocks[index];