Add graceful Ctrl+C shutdown: clean up worktrees on interrupt (#83)

Register SIGINT handler before worktree creation that cleans up all
worktrees and branches on Ctrl+C, then exits with code 130. Handler
is deregistered after normal run completion.

Generated by thinktank (5 agents, Agent #5 recommended — only agent
passing tests, +14/-1, focused single-file change).

Closes #60

Co-authored-by: unknown <that-github-user@github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

src/commands/run.ts

@@ -5,7 +5,7 @@ import { analyzeConvergence, recommend } from "../scoring/convergence.js";
 import { runTests } from "../scoring/test-runner.js";
 import type { AgentResult, EnsembleResult, RunOptions } from "../types.js";
 import { displayApplyInstructions, displayHeader, displayResults } from "../utils/display.js";
-import { cleanupBranches, createWorktree } from "../utils/git.js";
+import { cleanupBranches, createWorktree, removeWorktree } from "../utils/git.js";
 
 export async function run(opts: RunOptions): Promise<void> {
   displayHeader(opts.prompt, opts.attempts, opts.model);
@@ -33,6 +33,16 @@ export async function run(opts: RunOptions): Promise<void> {
   console.log("  Creating worktrees...");
   const worktrees: Array<{ id: number; path: string }> = [];
 
+  // Graceful Ctrl+C: clean up all worktrees created so far, then exit.
+  // Registered before worktree creation so any interrupt is handled.
+  const handleSigint = () => {
+    console.log("\n\n  Interrupted — cleaning up worktrees...");
+    Promise.all(worktrees.map(({ path }) => removeWorktree(path).catch(() => {})))
+      .then(() => cleanupBranches().catch(() => {}))
+      .then(() => process.exit(130));
+  };
+  process.on("SIGINT", handleSigint);
+
   for (let i = 1; i <= opts.attempts; i++) {
     const path = await createWorktree(i);
     worktrees.push({ id: i, path });
@@ -106,6 +116,9 @@ export async function run(opts: RunOptions): Promise<void> {
   // Save result to .thinktank/
   await saveResult(result);
 
+  // Deregister SIGINT handler — run completed normally, no cleanup needed.
+  process.removeListener("SIGINT", handleSigint);
+
   // Note: we intentionally do NOT clean up worktrees here so the user
   // can inspect them. They get cleaned up on next run.
 }