feat: add Browser Use CLI 3.0 skill

[MagMueller]

• A human has tested these changes.

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Why

OpenHands users can install Browser Use today, but the public extensions registry has no progressive-disclosure skill for the current CLI. This adds an opt-in path to direct CDP browser control without changing or removing the existing BrowserToolSet API.

Summary

• add a Browser Use CLI 3.0 skill with local and cloud browser workflows
• bootstrap the current CLI through an isolated uv tool install
• resolve the managed binary explicitly and strip inherited Python environment variables
• register the skill for OpenHands, Codex, and Claude discovery

Issue Number

No linked issue.

How to Test

1. Run uv sync --group test.
2. Run uv run pytest -q (542 passed, 6 skipped).
3. Run uv run python scripts/sync_extensions.py --check.
4. Smoke the documented CLI flow with uvx --from browser-use==0.13.7 browser-use; opening https://example.com returned Example Domain.

Video/Screenshots

Not included. This is an additive text-based skill and marketplace entry.

Notes

This PR intentionally leaves OpenHands' existing structured browser tools intact. A follow-up can run a matched BrowserToolSet-versus-CLI eval before proposing a default switch or deprecation path.

The explicit managed-binary path and clean Python child environment incorporate hardening learned from Hermes' Browser Use rollout: managed-first resolution and parent environment isolation.

Browser Use CLI 3.0 is the integration generation. The live smoke used browser-use==0.13.7, which currently bundles browser-harness==0.1.8.