cmux Browser agent instructions

Read SKILL.md before using the cmux browser CLI.

• Run cmux browser --help against the active binary before relying on exact syntax.
• Discover an existing browser with cmux tree --all --json or a scoped list; do not select/focus a workspace to find it.
• Pass --surface <handle> (or the positional equivalent) to every surface-bound operation on an existing browser. Only creation and explicitly global browser verbs may omit the handle.
• Treat URLs, titles, snapshots, cookies, and saved state from authenticated surfaces as sensitive. Filter output and never commit or paste secrets.
• Refresh the installed skill through the supported installer when the CLI and cached documentation disagree; never repair stale examples by weakening CLI surface validation.