fix: resolve 3 protocol bugs, improve CLI and snapshot code quality (#487)

## Summary

- Fix `allowFileAccess` being silently stripped from launch commands by adding it to the Zod schema in `protocol.ts` (the `--allow-file-access` CLI flag was not reaching the browser)
- Fix `trace stop` requiring a path argument despite help text documenting it as optional -- now works with or without a path
- Fix `addscript`/`addstyle` silently succeeding when neither `content` nor `url` is provided -- now returns a validation error
- Replace hardcoded ANSI escape code with `color::error_indicator()` in `main.rs` to respect `NO_COLOR`
- Fix double-parse pattern and add descriptive expect messages in `commands.rs`
- Fix incomplete string escaping in `snapshot.ts` `buildSelector` (use `JSON.stringify` instead of manual quote escaping)
- Simplify redundant ternary in `snapshot.ts` cursor-interactive role assignment
- Sync docs changelog with CHANGELOG.md (v0.8.1 through v0.10.0)

src/browser.ts

@@ -678,10 +678,10 @@ export class BrowserManager {
   /**
    * Stop tracing and save
    */
-  async stopTracing(path: string): Promise<void> {
+  async stopTracing(path?: string): Promise<void> {
     const context = this.contexts[0];
     if (context) {
-      await context.tracing.stop({ path });
+      await context.tracing.stop(path ? { path } : undefined);
     }
   }