Add customization and diagnostics skills

skills/cmux-customization/SKILL.md

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+---
+name: cmux-customization
+description: "Customize cmux for an end user. Use when changing cmux.json actions, custom commands, workspace layouts, Command Palette entries, surface toolbar buttons, shortcuts, notifications, browser routing, appearance, or Ghostty-backed terminal preferences."
+---
+
+# cmux Customization
+
+Use this skill for user-facing cmux customization. Keep the user's config intact, prefer schema-backed edits, and validate before reporting completion.
+
+## Choose the Right Surface
+
+- cmux app preferences: use `cmux-settings` for `~/.config/cmux/cmux.json` settings such as appearance, sidebar, notifications, browser behavior, automation, and shortcuts.
+- Custom actions, workspace layouts, toolbar buttons, plus-button behavior, and Command Palette entries: edit `~/.config/cmux/cmux.json` globally or `.cmux/cmux.json` in the project.
+- Terminal rendering and terminal keybindings: use Ghostty config, usually `~/.config/ghostty/config`. This includes fonts, cursor style, copy-on-select, shell integration, themes, and terminal keybindings.
+- Project-specific behavior: prefer `.cmux/cmux.json` in the project so the customization travels with the repo.
+
+If a request can be handled by Ghostty config, say that and use Ghostty config instead of inventing cmux UI settings.
+
+## Workflow
+
+1. Inspect existing config before editing.
+
+   ```bash
+   test -f ~/.config/cmux/cmux.json && sed -n '1,220p' ~/.config/cmux/cmux.json
+   test -f .cmux/cmux.json && sed -n '1,220p' .cmux/cmux.json
+   ```
+
+2. Pick global or project-local scope. Ask only when the choice changes behavior meaningfully. Default to project-local for repo-specific commands and global for app preferences.
+3. For app settings and cmux-owned shortcuts, use the settings helper from the installed skill or checkout:
+
+   ```bash
+   ~/.agents/skills/cmux-settings/scripts/cmux-settings list-supported
+   ~/.agents/skills/cmux-settings/scripts/cmux-settings set browser.openTerminalLinksInCmuxBrowser true
+   ~/.agents/skills/cmux-settings/scripts/cmux-settings validate
+   ```
+
+   If the user installed with `skills.sh`, use `~/.codex/skills/cmux-settings/scripts/cmux-settings` instead.
+4. For actions and workspace layouts, edit JSONC carefully. Preserve unrelated sections such as `vault`, `rightSidebar`, `commands`, `actions`, `ui`, and `notifications`.
+5. Reload config after successful edits:
+
+   ```bash
+   cmux reload-config
+   ```
+
+6. Verify the configured entrypoint exists. For shortcuts, read back the binding. For custom actions, confirm the action ID and where it should appear.
+
+## Common Patterns
+
+Add a Command Palette action that opens Codex in a new tab:
+
+```json
+{
+  "actions": {
+    "codex-new-tab": {
+      "type": "agent",
+      "agent": "codex",
+      "title": "Codex",
+      "subtitle": "Start Codex in this workspace",
+      "target": "newTabInCurrentPane",
+      "palette": true
+    }
+  }
+}
+```
+
+Add a project workspace layout:
+
+```json
+{
+  "commands": [
+    {
+      "name": "dev",
+      "type": "workspace",
+      "cwd": ".",
+      "layout": {
+        "type": "split",
+        "direction": "horizontal",
+        "children": [
+          { "type": "pane", "surfaces": [{ "type": "terminal", "command": "bun dev" }] },
+          { "type": "pane", "surfaces": [{ "type": "browser", "url": "http://localhost:3000" }] }
+        ]
+      }
+    }
+  ]
+}
+```
+
+Add surface toolbar buttons:
+
+```json
+{
+  "ui": {
+    "surfaceTabBar": {
+      "buttons": [
+        "cmux.newTerminal",
+        "cmux.newBrowser",
+        {
+          "action": "codex-new-tab",
+          "title": "Codex",
+          "icon": { "type": "symbol", "name": "terminal" }
+        }
+      ]
+    }
+  }
+}
+```
+
+## Validation
+
+- App settings: run `cmux-settings validate`.
+- JSONC shape: keep valid JSONC and avoid duplicate keys.
+- Runtime reload: run `cmux reload-config` when the CLI is available.
+- User-facing action: confirm the action title, shortcut, or toolbar placement the user asked for.
+
+## Rules
+
+- Do not overwrite whole top-level config sections unless you own the full section.
+- Do not store secrets directly in actions, commands, or prompts. Use environment variables or the user's secret manager.
+- Do not use app/runtime sleeps or timing workarounds in generated commands.
+- Do not add a cmux setting for behavior Ghostty already owns.
+- Keep labels short enough for menus, buttons, and the Command Palette.

skills/cmux-customization/agents/openai.yaml

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+interface:
+  display_name: "cmux Customization"
+  short_description: "Customize cmux actions, settings, and layouts."
+  default_prompt: "Use $cmux-customization to add a project-specific cmux action and validate the config."