fix(terminal): recover dropped keyCode 229 input

Android/GBoard-style keyboards fire keydown with keyCode 229 and, on some
paths, never mutate xterm's helper textarea. xterm has nothing to diff, so
it emits no data and the typed character is silently dropped: it never
reaches the PTY and never appears on screen.

terminal-keycode229-recovery.js is a standalone controller that re-emits
exactly those keys, and only once. xterm stays authoritative throughout:

- Only an explicit keyCode 229 keydown carrying a single printable key (or
  Enter) is eligible; Process/Unidentified/Dead, modifiers, AltGraph and a
  live composition are all left alone.
- The re-emit is scheduled from a microtask and then a zero-delay timer, so
  xterm's own textarea diff always gets the first opportunity; canonical
  data for the same key cancels the pending fallback.
- compositionstart and blur drop every pending candidate, so a real IME
  composition lifecycle is never second-guessed.
- After a recovery, one late canonical value attributed to that key token
  (via beforeinput/input on the helper textarea) is suppressed so the
  character cannot be delivered twice; the record expires after 250ms and
  an unattributed byte is never suppressed.

terminal-ui.js wires it at the two existing choke points — the custom key
handler and the onData registration, the latter now a named handler so the
recovery path can re-enter it — with both hooks wrapped so a failure in the
fallback can never break canonical input.

Unit coverage drives the module directly in a vm; the wiring itself is
covered end-to-end in the (browser-only) terminal-copy-shortcut suite.

src/web/public/terminal-ui.js

@@ -232,12 +232,22 @@ Object.assign(CodemanApp.prototype, {
   // Terminal Setup — xterm.js config and input handling
   // ═══════════════════════════════════════════════════════════════
 
+  _destroyKeyCode229Recovery() {
+    try {
+      this._keyCode229Recovery?.destroy?.();
+    } catch {
+      // Recovery is optional; terminal replacement must continue.
+    }
+    this._keyCode229Recovery = null;
+  },
+
   initTerminal() {
     // Load scrollback setting from localStorage, treating DEFAULT_SCROLLBACK as a floor
     // so users who picked up the previous (smaller) default get the new minimum on upgrade.
     const stored = parseInt(localStorage.getItem('codeman-scrollback'));
     const scrollback = Number.isFinite(stored) && stored > 0 ? Math.max(stored, DEFAULT_SCROLLBACK) : DEFAULT_SCROLLBACK;
 
+    this._destroyKeyCode229Recovery();
     this.terminal = new Terminal({
       theme: { ...window.codemanCurrentXtermTheme() },
       fontFamily: window.CodemanTerminalFont.resolve(this.loadAppSettingsFromStorage?.().terminalFontFamily),
@@ -292,6 +302,11 @@ Object.assign(CodemanApp.prototype, {
     // punctuation; returning false here would stop xterm before it can diff
     // the helper textarea and emit the committed Unicode text.
     this.terminal.attachCustomKeyEventHandler((ev) => {
+      try {
+        this._keyCode229Recovery?.handleKeyEvent?.(ev);
+      } catch {
+        // The fallback must never interfere with xterm's canonical handler.
+      }
       if (ev.isComposing || ev.key === 'Process' || ev.keyCode === 229) return true;
 
       // Let the app's Alt/Option session-nav and Command Palette shortcuts reach the document keydown handler
@@ -1026,7 +1041,14 @@ Object.assign(CodemanApp.prototype, {
     // mobile connections.  The overlay + localStorage persistence ensure input
     // survives tab switches and reconnects.
 
-    this.terminal.onData((data) => {
+    const handleTerminalData = (data, { recovered = false } = {}) => {
+      if (!recovered) {
+        try {
+          if (this._keyCode229Recovery?.consumeTerminalData?.(data)) return;
+        } catch {
+          // A broken dedupe guard must fail open to canonical xterm data.
+        }
+      }
       // Mouse SGR reports (tap-to-position) are NOT IME input — they must reach
       // the PTY even while the CJK input field owns focus. Without this exception
       // tapping to move the cursor silently does nothing whenever Chinese input
@@ -1348,7 +1370,21 @@ Object.assign(CodemanApp.prototype, {
           }
         }
       }
-    });
+    };
+
+    // Android/GBoard fires keydown with keyCode 229 and, on some paths, never
+    // mutates xterm's helper textarea, so the character is silently dropped.
+    // The controller re-emits exactly those keys, and only after xterm has had
+    // its own chance to produce the canonical data.
+    try {
+      this._keyCode229Recovery = window.CodemanKeyCode229Recovery?.create?.({
+        textarea: this.terminal.textarea,
+        emitRecovered: (data) => handleTerminalData(data, { recovered: true }),
+      });
+    } catch {
+      this._keyCode229Recovery = null;
+    }
+    this.terminal.onData((data) => handleTerminalData(data));
   },
 
   /**