refactor: consolidate shared packages and eliminate code duplication

- Update 26+ files to import secureFs from @automaker/platform
- Create shared type files: github.ts, worktree.ts, claude.ts in libs/types
- Create exec-utils.ts for cross-platform shell execution
- Delete redundant wrapper files: secure-fs.ts, stream-processor.ts, enhancement-prompts.ts
- Update GitHub routes to use createLogError pattern
- Add isENOENT helper to routes/common.ts
- Fix test imports to use @automaker/prompts and @automaker/platform

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/server/tests/unit/services/dev-server-service.test.ts

@@ -10,10 +10,16 @@ vi.mock('child_process', () => ({
   execSync: vi.fn(),
 }));
 
-// Mock secure-fs
-vi.mock('@/lib/secure-fs.js', () => ({
-  access: vi.fn(),
-}));
+// Mock secure-fs from @automaker/platform
+vi.mock('@automaker/platform', async () => {
+  const actual = await vi.importActual('@automaker/platform');
+  return {
+    ...actual,
+    secureFs: {
+      access: vi.fn(),
+    },
+  };
+});
 
 // Mock net
 vi.mock('net', () => ({
@@ -24,7 +30,7 @@ vi.mock('net', () => ({
 }));
 
 import { spawn, execSync } from 'child_process';
-import * as secureFs from '@/lib/secure-fs.js';
+import { secureFs } from '@automaker/platform';
 import net from 'net';
 
 describe('dev-server-service.ts', () => {