fix(predictive-echo): anchor hold after unpredicted wire edits (review findings)

Independent post-build review found three gaps, all one family: input that
changes the composer without a prediction leaves the DISPLAYED cursor stale
for one RTT, and anchoring a new run on it painted ghosts one cell off
(blank-neutral, so they lived out the full TTL: "tehh" on
backspace-then-retype, exactly on the links the feature targets).

Fix: the addon now HOLDS new predictions after any such edit (backspace with
nothing outstanding = deleting echoed text, clearPredictions, and now also
IME/plain-paste 'text' commits, which the hook clears like 'clear') until
the next PARSED write releases the hold. The inline predictChar reconcile
deliberately does not count: only the emitter pass or the public
reconcile() is the display-caught-up contract. Worst case is exactly one
unpredicted keystroke, whose own echo releases the hold. Also patched the
one bypass path the PR had missed: _handleCjkInput now clears predictions
like insertTerminalText and the other bypass sends.

Package suite 230, vm gating 85, E2E 10/10 all green after the change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/xterm-zerolag-input/test/codex-replay.test.ts

@@ -62,7 +62,7 @@ async function replay(name: string) {
       let painted = false;
       if (kind === 'char') painted = addon.predictChar(line.data);
       else if (kind === 'backspace') addon.predictBackspace();
-      else if (kind === 'clear') addon.clearPredictions();
+      else addon.clearPredictions(); // 'clear' AND 'text', like the terminal-ui hook
       // Span/record parity and grid bounds hold at every step
       expect(rt.spanCount()).toBe(addon.state.outstanding);
       assertSpansInGrid(rt);

packages/xterm-zerolag-input/test/predictive-echo-addon.test.ts

@@ -335,6 +335,7 @@ describe('PredictiveEchoAddon', () => {
 
   it('predictBackspace pops newest, returns false when empty, never touches confirmed', async () => {
     expect(addon.predictBackspace()).toBe(false);
+    addon.reconcile(); // the empty pop armed the anchor hold; release it
     addon.predictChar('a');
     addon.predictChar('b');
     expect(addon.predictBackspace()).toBe(true);
@@ -478,6 +479,7 @@ describe('PredictiveEchoAddon', () => {
     rows.style.color = 'rgb(255, 0, 0)'; // skin change
     a.refreshFont();
     a.clearPredictions();
+    a.reconcile(); // release the anchor hold armed by the clear
     a.predictChar('v');
     const span2 = themed.terminal.element.querySelector('.xterm-screen span') as HTMLSpanElement;
     expect(span2.style.color).toBe('rgb(255, 0, 0)');
@@ -485,6 +487,37 @@ describe('PredictiveEchoAddon', () => {
     themed.cleanup();
   });
 
+  it('anchor hold: backspace into echoed text suppresses prediction until a write parses', async () => {
+    // \x7f went to the wire with nothing outstanding: the cursor will move
+    // in a way the display has not shown, so anchoring now paints one cell
+    // off (review finding: "tehh" ghosts on backspace-then-retype at RTT)
+    expect(addon.predictBackspace()).toBe(false);
+    expect(addon.predictChar('x')).toBe(false);
+    expect(spansOf(mock)).toHaveLength(0);
+    mock.fireWriteParsed(); // the display caught up
+    await flushMicrotasks();
+    expect(addon.predictChar('x')).toBe(true);
+  });
+
+  it('anchor hold: clearPredictions suppresses until a write parses (or manual reconcile)', async () => {
+    addon.predictChar('a');
+    addon.clearPredictions(); // consumer saw Enter/Esc/arrow/paste
+    expect(addon.predictChar('b')).toBe(false);
+    mock.fireWriteParsed();
+    await flushMicrotasks();
+    expect(addon.predictChar('b')).toBe(true);
+  });
+
+  it('anchor hold: the inline predictChar reconcile does NOT release it', () => {
+    addon.clearPredictions();
+    // Several keystrokes in a row before any echo: all suppressed, because
+    // predictChar's inline pass must not count as the display catching up
+    expect(addon.predictChar('a')).toBe(false);
+    expect(addon.predictChar('b')).toBe(false);
+    addon.reconcile(); // public/manual pass IS the caught-up contract
+    expect(addon.predictChar('c')).toBe(true);
+  });
+
   it('state getter reports outstanding/confirmedTotal/droppedTotal/anchor', async () => {
     expect(addon.state).toEqual({ outstanding: 0, confirmedTotal: 0, droppedTotal: 0, anchor: null });
     addon.predictChar('a');