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.

src/browser.ts

@@ -682,6 +682,7 @@ export class BrowserManager {
           args: [`--disable-extensions-except=${extPaths}`, `--load-extension=${extPaths}`],
           viewport,
           extraHTTPHeaders: options.headers,
+          ...(options.proxy && { proxy: options.proxy }),
         }
       );
       this.isPersistentContext = true;
@@ -691,10 +692,14 @@ export class BrowserManager {
         executablePath: options.executablePath,
       });
       this.cdpPort = null;
-      context = await this.browser.newContext({ viewport, extraHTTPHeaders: options.headers });
+      context = await this.browser.newContext({
+        viewport,
+        extraHTTPHeaders: options.headers,
+        ...(options.proxy && { proxy: options.proxy }),
+      });
     }
 
-    context.setDefaultTimeout(10000);
+    context.setDefaultTimeout(60000);
     this.contexts.push(context);
 
     const page = context.pages()[0] ?? (await context.newPage());
@@ -828,7 +833,7 @@ export class BrowserManager {
     const context = await this.browser.newContext({
       viewport: viewport ?? { width: 1280, height: 720 },
     });
-    context.setDefaultTimeout(10000);
+    context.setDefaultTimeout(60000);
     this.contexts.push(context);
 
     const page = await context.newPage();