feat: add --proxy flag for browser proxy configuration (#16)

* feat: add --proxy flag for browser proxy support

Add CLI flag to configure HTTP/SOCKS proxy for Playwright browser context.
Supports URL format with optional credentials: http://user:pass@host:port

* fix: improve proxy parsing error handling

- Handle malformed credentials (@ without :) by ignoring incomplete creds
- Replace unwrap() with expect() for better error messages
- Addresses Vercel bot code review suggestions

* Restaura cambios locales: soporte AGENT_BROWSER_HOME y timeout aumentado

- Agrega soporte para variable de entorno AGENT_BROWSER_HOME en connection.rs
- Aumenta timeout por defecto de 10s a 60s para conexiones más lentas

* feat: add --proxy flag for browser proxy configuration

Implements proxy support based on PR #16 with reviewer feedback:

Features:
- Parse proxy URLs: http://[user:pass@]host:port
- Support for HTTP, HTTPS, and SOCKS5 protocols
- Handle username-only auth (preserves username with empty password)
- Apply proxy to both standard and persistent contexts

Changes:
- cli/src/flags.rs: Add proxy flag parsing
- cli/src/main.rs: Add parse_proxy() with comprehensive tests
- cli/src/output.rs: Add --proxy to help output
- cli/src/commands.rs: Fix test helper to include proxy field
- src/types.ts: Add proxy to LaunchCommand interface
- src/protocol.ts: Add proxy validation schema
- src/browser.ts: Apply proxy to context creation

Tests:
- 7 unit tests for parse_proxy() covering all edge cases
- All Rust tests passing (69 tests)
- All TypeScript tests passing (168 tests)
- TypeScript typecheck passing

Resolves feedback from PR #16:
- Fixed username-only proxy handling (issue #2681046975)
- Added comprehensive unit tests
- Added --proxy to help documentation
- Used expect() instead of unwrap() for better error messages

* refactor: simplify parse_proxy function

- Remove redundant comments
- Extract server variable to reduce duplication
- Inline trivial username/password variables

All 7 proxy tests still passing.

cli/src/connection.rs

@@ -174,16 +174,23 @@ pub fn ensure_daemon(
     let exe_path = env::current_exe().map_err(|e| e.to_string())?;
     let exe_dir = exe_path.parent().unwrap();
 
-    let daemon_paths = [
+    let mut daemon_paths = vec![
         exe_dir.join("daemon.js"),
         exe_dir.join("../dist/daemon.js"),
         PathBuf::from("dist/daemon.js"),
     ];
 
+    // Check AGENT_BROWSER_HOME environment variable
+    if let Ok(home) = env::var("AGENT_BROWSER_HOME") {
+        let home_path = PathBuf::from(&home);
+        daemon_paths.insert(0, home_path.join("dist/daemon.js"));
+        daemon_paths.insert(1, home_path.join("daemon.js"));
+    }
+
     let daemon_path = daemon_paths
         .iter()
         .find(|p| p.exists())
-        .ok_or("Daemon not found. Run from project directory or ensure daemon.js is alongside binary.")?;
+        .ok_or("Daemon not found. Set AGENT_BROWSER_HOME environment variable or run from project directory.")?;
 
     // Spawn daemon as a fully detached background process
     #[cfg(unix)]