fix: symlink node_modules in worktree for test execution

Worktrees don't share node_modules with the main repo.
Now symlinks both root and api/node_modules so npm test
works in the worktree without a full npm install.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: recuu-pfeg

src/spawner.ts

@@ -1,6 +1,6 @@
 import { spawn, type ChildProcess } from "node:child_process";
 import { execSync } from "node:child_process";
-import { rmSync, existsSync, mkdirSync } from "node:fs";
+import { rmSync, existsSync, mkdirSync, symlinkSync } from "node:fs";
 import path from "node:path";
 import type { AgentConfig, RunningAgent } from "./types.js";
 import { getTerminal, buildShellCommand, type TerminalInfo } from "./terminal.js";
@@ -56,6 +56,22 @@ export function createWorktree(
     return repoDir;
   }
 
+  // Symlink node_modules from main repo so tests and builds work in worktree
+  try {
+    const mainNodeModules = path.join(repoDir, "node_modules");
+    const wtNodeModules = path.join(worktreeDir, "node_modules");
+    if (existsSync(mainNodeModules) && !existsSync(wtNodeModules)) {
+      symlinkSync(mainNodeModules, wtNodeModules, "dir");
+    }
+    // Also symlink api/node_modules if it exists (monorepo)
+    const apiMainNm = path.join(repoDir, "api", "node_modules");
+    const apiWtDir = path.join(worktreeDir, "api");
+    const apiWtNm = path.join(apiWtDir, "node_modules");
+    if (existsSync(apiMainNm) && existsSync(apiWtDir) && !existsSync(apiWtNm)) {
+      symlinkSync(apiMainNm, apiWtNm, "dir");
+    }
+  } catch { /* non-fatal — tests may fail but agent can still work */ }
+
   return worktreeDir;
 }