fix(cli): pass custom Chrome args to local launches

[luochen211]

Summary

• pass custom Chromium args through local isolated browse launches
• read optional args from BROWSE_CHROME_ARGS in the browse daemon
• cover isolated and auto-fallback launch strategies with regression tests

Fixes #2148

Tests

• pnpm --dir packages/cli test tests/local-strategy.test.ts
• pnpm exec prettier --check packages/cli/src/local-strategy.ts packages/cli/tests/local-strategy.test.ts packages/cli/src/index.ts
• pnpm --dir packages/cli run eslint
• pnpm --dir packages/cli run typecheck
• git diff --check

---

Summary by cubic

Allow passing custom Chrome/Chromium flags to managed local browse sessions. We use target.chromeArgs when provided or read BROWSE_CHROME_ARGS and forward them to localBrowserLaunchOptions.args.

• New Features
  • Parse BROWSE_CHROME_ARGS as JSON array or space-separated string.
  • For managed-local only: prefer target.chromeArgs; otherwise use the env var.
  • No args are sent if both sources are unset.

^{Written for commit a5d96e3. Summary will update on new commits.}

[changeset-bot]

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Latest commit: a5d96e3

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[github-actions]

This PR is from an external contributor and must be approved by a stagehand team member with write access before CI can run.
Approving the latest commit mirrors it into an internal PR owned by the approver.
If new commits are pushed later, the internal PR stays open but is marked stale until someone approves the latest external commit and refreshes it.

[luochen211]

Retargeted this PR to v3: main moved to Stagehand v4 in #2671 and removed the v3 browse CLI, while v3 is now the maintained base for this code. The PR is mergeable again and its diff remains limited to the original browse implementation and regression test.\n\nValidation against current v3:\n- pnpm exec turbo run build --filter=browse (4/4 tasks)\n- pnpm --dir packages/cli test tests/driver-foundation.test.ts (37/37 tests)\n- pnpm --dir packages/cli lint\n- git diff --check\n\nNo changeset is added because browse is explicitly ignored by .changeset/config.json and uses its separate release flow.