pi-plan: plan-mode goals + evidence in one plan.md, subagent sign-off

Small, guide-not-gate plan/goal tracker for pi. The agent edits plan.md with
its normal Edit tool; CompleteGoal is the one blessed path that runs verify +
a read-only judge and records the result. Plan mode drafts goals (done_when +
failure_modes + subtasks), a per-turn injection keeps the active goal alive
through compaction, and a reminder drives upkeep + autonomy.

- src/plan-file.ts: pure parse + the two writes CompleteGoal needs + recordSignOff
- src/index.ts: plan mode, review menu, injection, reminder, widget, CompleteGoal, oracle spawn
- src/prompts.ts: all model-facing text in flow order
- test/: 15 unit tests (parser, disambiguation, sign-off record logic)

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ES2022",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "jsx": "react-jsx",
+    "outDir": "dist",
+    "rootDir": "src",
+    "declaration": true
+  },
+  "include": ["src/**/*.ts", "src/**/*.tsx"]
+}