feat(predictive-echo): Phase 0 codex fixtures, measurements, package scaffolding

Recorder (scripts/dev/record-codex-frames.mjs) captures real codex 0.147
TUI output through the production pipeline (tmux status-off + the codex-mode
full strip from session.ts) into JSONL fixtures with keystroke injection
points; analyzer replays them through @xterm/headless for the measurements
in docs/predictive-echo-plan.md. Composer signature /^> /-style (U+203A),
modal and wrapped rows correctly rejected, echo is unstyled default-fg,
tmux delivers echo as minimal in-place deltas.

Package: types.ts gains optional cursorX/cursorY, getCell, onWriteParsed,
onResize (all additive); prediction-renderer.ts renders per-glyph spans
keyed by prediction seq; @xterm/headless@^6.0.0 devDep for replay tests.

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

package-lock.json

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       "license": "MIT"
     },
+    "node_modules/@xterm/headless": {
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+      "resolved": "https://registry.npmjs.org/@xterm/headless/-/headless-6.0.0.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "workspaces": [
+        "addons/*"
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@@ -12336,6 +12346,7 @@
       "version": "0.1.8",
       "license": "MIT",
       "devDependencies": {
+        "@xterm/headless": "^6.0.0",
         "jsdom": "^24.1.3",
         "tsup": "^8.5.1",
         "typescript": "^5.5.0",