Rename express/ to backend/ and update references

Update paths in sync.sh, master/main.go, and CLAUDE.md to reflect
the directory rename.

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

CLAUDE.md

@@ -38,7 +38,7 @@ master process. Key design principles:
 
 **Format TypeScript code:**
 ```bash
-cd express && ../cmd pnpm biome check --write .
+cd backend && ../cmd pnpm biome check --write .
 ```
 
 **Build Go master process:**
@@ -54,7 +54,7 @@ cd master && go build
 
 ### Components
 
-- **express/** - TypeScript/Express.js backend application
+- **backend/** - TypeScript/Express.js backend application
 - **master/** - Go-based master process for file watching and process management
 - **framework/** - Managed binaries (Node.js, pnpm), command wrappers, and
   framework-specific library code
@@ -68,7 +68,7 @@ Responsibilities:
 - Proxy web requests to backend workers
 - Behaves identically in all environments (no dev/prod distinction)
 
-### Express App Structure
+### Backend App Structure
 
 - `app.ts` - Main Express application setup with route matching
 - `routes.ts` - Route definitions

master/main.go

@@ -9,7 +9,7 @@ import (
 )
 
 func main() {
-	watchDir := flag.String("watch", "../express", "directory to watch for changes")
+	watchDir := flag.String("watch", "../backend", "directory to watch for changes")
 	workers := flag.Int("workers", 1, "number of worker processes")
 	basePort := flag.Int("base-port", 3000, "base port for worker processes")
 	listenPort := flag.Int("port", 8080, "port for the reverse proxy to listen on")

sync.sh

@@ -79,5 +79,5 @@ cd "$DIR/logger"
 go build
 
 # Update framework code
-cd "$DIR/express"
+cd "$DIR/backend"
 ../cmd pnpm install