docs: route browser-launching tests to containers; forbid host Keychain access

[suchintan]

https://github.com/Skyvern-AI/rustwright-cloud/pull/219

[claude]

Summary

Docs-only change to AGENTS.md (agent/contributor instructions, not user-facing docs): routes browser-launching tests to containers and adds a rule that Chromium launches must never touch the host macOS Keychain. The writing is clear and the intent (avoid Keychain prompts stalling a host run) is sound, but the new rule asserts an invariant that the codebase doesn't currently satisfy.

🔴 Critical Issues (0)

None.

🟡 Suggestions (1)

• The stated requirement isn't actually true of the code yet. AGENTS.md:80-83 says the library's default_args "must pass --use-mock-keychain and --password-store=basic," framing it as an existing compatibility requirement ("Upstream Playwright sets both by default"). But default_args in src/lib.rs (~line 25826) has no such flags today, and a repo-wide grep for use-mock-keychain/password-store turns up zero hits anywhere in src/, benchmarks/, or tools/. As written, this doc will make a future agent believe the Keychain-safety behavior already exists and is just a rule to maintain, when in fact every host Chromium launch in this repo currently risks a Keychain prompt on macOS — the actual code fix hasn't landed. Consider either (a) landing the --use-mock-keychain/--password-store=basic additions to default_args (and the benchmark/tool launchers) in this PR or a fast-follow, or (b) rephrasing the doc to make clear this is a gap to close rather than an already-enforced invariant, so agents don't skip fixing it.

📝 Minor / Style (0)

None.