feat(predictive-echo): second vendor bundle wiring

postinstall + build.mjs build vendor/xterm-predictive-echo.js as a SEPARATE
IIFE (window.PredictiveEchoAddon + self-activating PredictiveEchoOverlay);
the zerolag bundle command is untouched and its output verified
sha256-identical. index.html loads it after the zerolag tag (cacheBustAssets
covers it), sw.js precaches it, build.mjs HASHABLE content-hashes it.
A missing or broken bundle degrades codex to plain PTY echo.

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

src/web/public/index.html

@@ -38,6 +38,7 @@
   <!-- WebGL addon lazy-loaded by app.js on desktop only (skipped on mobile, saving 244KB) -->
   <script defer src="vendor/xterm-addon-unicode11.min.js"></script>
   <script defer src="vendor/xterm-zerolag-input.js"></script>
+  <script defer src="vendor/xterm-predictive-echo.js"></script>
   <script defer src="vendor/marked.min.js"></script>
   <!-- DOMPurify (allowlist HTML sanitizer for rendered markdown).
        Must load before sanitize-html.js (which wires it) and app.js (which calls it). -->

src/web/public/sw.js

@@ -40,6 +40,7 @@ const APP_SHELL = [
   '/vendor/xterm-addon-fit.min.js',
   '/vendor/xterm-addon-unicode11.min.js',
   '/vendor/xterm-zerolag-input.js',
+  '/vendor/xterm-predictive-echo.js',
   '/vendor/xterm.css',
   '/icon-192.png',
   '/icon-512.png',