Display Markdown files in cmux without blank panes

Fixes a specific cmux bug: cmux markdown open always spawns a brand-new pane, even with --direction right, and the common workaround of moving that markdown surface into an existing right pane via move-surface renders it blank - the surface keeps type=markdown and looks healthy but shows nothing. This skill gives the two reliable ways around that bug instead of the broken move-surface path.

Use it when opening Markdown in cmux shows a blank pane or the wrong layout, or when you need to display a Markdown file in a stable cmux right pane. Never move-surface a markdown viewer - that is exactly the path that bugs out and is the core reason this skill exists. Only close panes that are unused or irrelevant; never close a pane the user is actively working in.

Option A - open it right on the first try, when there is no usable right pane yet: let cmux create one and leave it where it lands, then do NOT move it:

cmux markdown open /abs/path/file.md --direction right --focus false

Option B - if other, unused or irrelevant right panes are in the way, close them first, then open the markdown fresh so it creates its own clean right pane:

cmux list-panes --workspace "$CMUX_WORKSPACE_ID"
cmux list-pane-surfaces --pane pane:NN
cmux close-surface --surface surface:XX     # repeat per surface in that pane
cmux markdown open /abs/path/file.md --direction right --focus false

If it spawned where you wanted it, you're done - no further action needed either way. Output is a markdown viewer rendered in a stable right pane - always anchored to $CMUX_WORKSPACE_ID rather than whichever workspace is visually focused, and opened with --focus false so it doesn't steal the user's focus. There is no way to screenshot or read a markdown surface to verify it rendered; if unsure, ask the user.

Wraps cmux's own pane and surface commands (markdown open, list-panes, list-pane-surfaces, close-surface) and is adapted from davidondrej/skills. Verify local paths, tools, credentials, and agent features before acting, and for any commands, remote access, scheduling, browser automation, or file-changing workflows it triggers, get explicit user approval and confirm the target environment first.

Agents and developers working inside cmux who need a markdown file displayed reliably in a right pane, rather than fighting a stray extra pane or a viewer that silently renders blank after being moved.