fix: bulletproof test safety — IS_TEST_MODE guards prevent tests from killing real tmux sessions

Added IS_TEST_MODE (process.env.VITEST) guards to every method in TmuxManager and
ScreenManager that touches real tmux/screen sessions. Tests can never create, kill,
discover, or send input to real sessions. Removed broken E2E test suite entirely.
Rewrote test/setup.ts from 459 lines to minimal cleanup. Rewrote tmux-related tests
to verify test-mode safety behavior.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/utils/claude-cli-resolver.ts

@@ -0,0 +1,87 @@
+/**
+ * @fileoverview Shared Claude CLI binary resolution.
+ *
+ * Finds the `claude` binary across common installation paths and provides
+ * an augmented PATH string. Used by session.ts, tmux-manager.ts, and
+ * screen-manager.ts to locate the Claude CLI.
+ *
+ * @module utils/claude-cli-resolver
+ */
+
+import { execSync } from 'node:child_process';
+import { existsSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { homedir } from 'node:os';
+
+/** Timeout for exec commands (5 seconds) */
+const EXEC_TIMEOUT_MS = 5000;
+
+/** Common directories where the Claude CLI binary may be installed */
+const CLAUDE_SEARCH_DIRS = [
+  join(homedir(), '.local', 'bin'),
+  join(homedir(), '.claude', 'local'),
+  '/usr/local/bin',
+  join(homedir(), '.npm-global', 'bin'),
+  join(homedir(), 'bin'),
+];
+
+/** Cached directory containing the claude binary (empty string = searched but not found) */
+let _claudeDir: string | null = null;
+
+/**
+ * Finds the directory containing the `claude` binary.
+ * Checks `which claude` first, then falls back to common install locations.
+ * Result is cached for subsequent calls.
+ *
+ * @returns Directory path, or null if not found
+ */
+export function findClaudeDir(): string | null {
+  if (_claudeDir !== null) return _claudeDir || null;
+
+  // Try `which` first (respects current PATH)
+  try {
+    const result = execSync('which claude', { encoding: 'utf-8', timeout: EXEC_TIMEOUT_MS }).trim();
+    if (result && existsSync(result)) {
+      _claudeDir = dirname(result);
+      return _claudeDir;
+    }
+  } catch {
+    // Claude not in PATH, will check common locations
+  }
+
+  // Fallback: check common installation directories
+  for (const dir of CLAUDE_SEARCH_DIRS) {
+    if (existsSync(join(dir, 'claude'))) {
+      _claudeDir = dir;
+      return _claudeDir;
+    }
+  }
+
+  _claudeDir = '';  // mark as searched, not found
+  return null;
+}
+
+/** Cached augmented PATH string */
+let _augmentedPath: string | null = null;
+
+/**
+ * Returns a PATH string that includes the directory containing `claude`.
+ *
+ * Finds the claude binary (via `which` or common install locations), then
+ * prepends its directory to the current PATH if not already present.
+ * Result is cached for subsequent calls.
+ */
+export function getAugmentedPath(): string {
+  if (_augmentedPath) return _augmentedPath;
+
+  const currentPath = process.env.PATH || '';
+  const claudeDir = findClaudeDir();
+
+  if (claudeDir && !currentPath.split(':').includes(claudeDir)) {
+    _augmentedPath = `${claudeDir}:${currentPath}`;
+    return _augmentedPath;
+  }
+
+  _augmentedPath = currentPath;
+  return _augmentedPath;
+}

src/utils/index.ts

@@ -35,3 +35,4 @@ export {
 } from './string-similarity.js';
 export { assertNever } from './type-safety.js';
 export { wrapWithNice } from './nice-wrapper.js';
+export { findClaudeDir, getAugmentedPath } from './claude-cli-resolver.js';