Submit mobile-harness to anthropics/claude-plugins-community

Submit droidrun/mobile-harness to the claude-plugins-community marketplace (self-serve submission; Anthropic runs automated validation and safety screening; docs: https://code.claude.com/docs/en/discover-plugins).

Notes:

• The repo qualifies as a skill-bundle (root SKILL.md, no secrets, passing Gen/Socket/Snyk audits on skills.sh).
• Accepted plugins are pinned to a commit SHA — plan a re-submission cadence (e.g. after significant guide changes) so installs don't go stale.