refactor: pass 2 — extract shared helpers and simplify patterns

app.js:
- Add _clearTimer() helper replacing 11 inline clearTimeout patterns
- Add _isStaleSelect() helper for generation check + cleanup
- Replace 11 keyboard shortcut if-blocks with data-driven lookup table
- Extract _cleanupPreviousSession() from selectSession() (~75 lines)
- Extract _resetAllAppState() from handleInit() (~75 lines)

tmux-manager:
- Extract buildEnvExports() eliminating duplication in createSession/respawnPane
- Extract buildPathExport() for CLI path resolution
- Extract _configureOpenCode() for OpenCode setup

routes:
- Add readJsonConfig() to route-helpers, replacing 5 inline JSON-read patterns
- Add validateSessionFilePath() to route-helpers, replacing 2 identical path
  traversal validation blocks in file-routes

session-auto-ops:
- Convert executeWhenIdle() from 8 positional params to options object
- Extract validateThreshold() for shared compact/clear validation

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

src/web/routes/case-routes.ts

@@ -14,7 +14,7 @@ import { ApiErrorCode, createErrorResponse, getErrorMessage } from '../../types.
 import { CreateCaseSchema, LinkCaseSchema } from '../schemas.js';
 import { generateClaudeMd } from '../../templates/claude-md.js';
 import { writeHooksConfig } from '../../hooks-config.js';
-import { CASES_DIR, validatePathWithinBase, parseBody } from '../route-helpers.js';
+import { CASES_DIR, validatePathWithinBase, parseBody, readJsonConfig } from '../route-helpers.js';
 import { SseEvent } from '../sse-events.js';
 import type { EventPort, ConfigPort } from '../ports/index.js';
 
@@ -22,15 +22,7 @@ const LINKED_CASES_FILE = join(homedir(), '.codeman', 'linked-cases.json');
 
 /** Read and parse linked-cases.json, returning empty object on missing/invalid file. */
 async function readLinkedCases(): Promise<Record<string, string>> {
-  try {
-    return JSON.parse(await fs.readFile(LINKED_CASES_FILE, 'utf-8'));
-  } catch (err) {
-    // Only warn on real I/O errors, not ENOENT (file missing) or SyntaxError (corrupted JSON)
-    if ((err as NodeJS.ErrnoException).code && (err as NodeJS.ErrnoException).code !== 'ENOENT') {
-      console.warn('[Server] Failed to read linked cases:', err);
-    }
-    return {};
-  }
+  return readJsonConfig<Record<string, string>>(LINKED_CASES_FILE, 'linked cases', {});
 }
 
 /** Resolve a case name to its directory path, checking linked cases first, then CASES_DIR. */

src/web/routes/file-routes.ts

@@ -4,12 +4,11 @@
  */
 
 import { FastifyInstance } from 'fastify';
-import { join, resolve, relative, isAbsolute } from 'node:path';
-import { realpathSync } from 'node:fs';
+import { join } from 'node:path';
 import fs from 'node:fs/promises';
 import { ApiErrorCode, createErrorResponse, getErrorMessage } from '../../types.js';
 import { fileStreamManager } from '../../file-stream-manager.js';
-import { findSessionOrFail } from '../route-helpers.js';
+import { findSessionOrFail, validateSessionFilePath } from '../route-helpers.js';
 import type { SessionPort } from '../ports/index.js';
 
 export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void {
@@ -148,17 +147,11 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void
     }
 
     // Validate path is within working directory (security: resolve symlinks to prevent traversal)
-    const fullPath = resolve(session.workingDir, filePath);
-    let resolvedPath: string;
-    try {
-      resolvedPath = realpathSync(fullPath);
-    } catch {
+    const validated = validateSessionFilePath(session.workingDir, filePath);
+    if (!validated) {
       return createErrorResponse(ApiErrorCode.NOT_FOUND, 'File not found');
     }
-    const relativePath = relative(session.workingDir, resolvedPath);
-    if (relativePath.startsWith('..') || isAbsolute(relativePath)) {
-      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Path must be within working directory');
-    }
+    const { resolvedPath } = validated;
 
     try {
       const stat = await fs.stat(resolvedPath);
@@ -255,19 +248,12 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void
     }
 
     // Validate path is within working directory (security: resolve symlinks to prevent traversal)
-    const fullPath = resolve(session.workingDir, filePath);
-    let resolvedPath: string;
-    try {
-      resolvedPath = realpathSync(fullPath);
-    } catch {
+    const validated = validateSessionFilePath(session.workingDir, filePath);
+    if (!validated) {
       reply.code(404).send(createErrorResponse(ApiErrorCode.NOT_FOUND, 'File not found'));
       return;
     }
-    const relativePath = relative(session.workingDir, resolvedPath);
-    if (relativePath.startsWith('..') || isAbsolute(relativePath)) {
-      reply.code(400).send(createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Path must be within working directory'));
-      return;
-    }
+    const { resolvedPath } = validated;
 
     try {
       // Validate file size before reading (DoS protection - prevent memory exhaustion)

src/web/routes/system-routes.ts

@@ -24,7 +24,7 @@ import {
 import { subagentWatcher } from '../../subagent-watcher.js';
 import { imageWatcher } from '../../image-watcher.js';
 import { getLifecycleLog } from '../../session-lifecycle-log.js';
-import { findSessionOrFail, formatUptime, parseBody, SETTINGS_PATH } from '../route-helpers.js';
+import { findSessionOrFail, formatUptime, parseBody, readJsonConfig, SETTINGS_PATH } from '../route-helpers.js';
 import { SseEvent } from '../sse-events.js';
 import type { SessionPort, EventPort, ConfigPort, InfraPort, AuthPort } from '../ports/index.js';
 import { AUTH_COOKIE_NAME } from '../middleware/auth.js';
@@ -393,15 +393,7 @@ export function registerSystemRoutes(
   // ========== Settings ==========
 
   app.get('/api/settings', async () => {
-    try {
-      const content = await fs.readFile(SETTINGS_PATH, 'utf-8');
-      return JSON.parse(content);
-    } catch (err) {
-      if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
-        console.error('Failed to read settings:', err);
-      }
-    }
-    return {};
+    return readJsonConfig(SETTINGS_PATH, 'settings', {});
   });
 
   app.put('/api/settings', async (req) => {
@@ -472,16 +464,8 @@ export function registerSystemRoutes(
   // ========== Model Configuration ==========
 
   app.get('/api/execution/model-config', async () => {
-    try {
-      const content = await fs.readFile(SETTINGS_PATH, 'utf-8');
-      const settings = JSON.parse(content);
-      return { success: true, data: settings.modelConfig || {} };
-    } catch (err) {
-      if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
-        console.error('Failed to read model config:', err);
-      }
-      return { success: true, data: {} };
-    }
+    const settings = await readJsonConfig<Record<string, unknown>>(SETTINGS_PATH, 'model config', {});
+    return { success: true, data: settings.modelConfig || {} };
   });
 
   app.put('/api/execution/model-config', async (req) => {
@@ -545,15 +529,7 @@ export function registerSystemRoutes(
   // ========== Subagent Window State Persistence ==========
 
   app.get('/api/subagent-window-states', async () => {
-    try {
-      const content = await fs.readFile(windowStatesPath, 'utf-8');
-      return JSON.parse(content);
-    } catch (err) {
-      if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
-        console.error('Failed to read subagent window states:', err);
-      }
-    }
-    return { minimized: {}, open: [] };
+    return readJsonConfig(windowStatesPath, 'subagent window states', { minimized: {}, open: [] });
   });
 
   app.put('/api/subagent-window-states', async (req) => {
@@ -573,15 +549,7 @@ export function registerSystemRoutes(
   // ========== Subagent Parent Associations ==========
 
   app.get('/api/subagent-parents', async () => {
-    try {
-      const content = await fs.readFile(parentMapPath, 'utf-8');
-      return JSON.parse(content);
-    } catch (err) {
-      if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
-        console.error('Failed to read subagent parent map:', err);
-      }
-    }
-    return {};
+    return readJsonConfig(parentMapPath, 'subagent parent map', {});
   });
 
   app.put('/api/subagent-parents', async (req) => {