### Summary

Google Antigravity CLI (`agy`) is currently missing from Omarchy's default agent ecosystem. Running `omarchy default agent antigravity` or selecting it as default is unsupported, and the status bar's `omarchy.agents` panel lacks built-in discovery for Antigravity quotas and sessions.

Adding native support would allow users to install and manage `agy` through `mise` and use it seamlessly alongside Claude, Codex, Gemini, etc.

---

### Proposed Implementation

1. **Default Agent Resolver (`bin/omarchy-default-agent`)**
   Add `agy` / `antigravity` to the CLI argument parser and `mise` package resolution:
   ```bash
   agy | antigravity)
     agent="agy"
     name="Antigravity"
     ;;
   ```

2. **Unattended & Prompt Launcher (`bin/omarchy-agent`)**
   Map `agy` flags to match Omarchy's headless launcher contract (`--dangerously-skip-permissions` for unattended execution, and `--prompt-interactive` for prompts):
   ```bash
   agy)
     command=(agy --dangerously-skip-permissions)
     [[ -n ${prompt:-} ]] && command+=(--prompt-interactive "$prompt")
     ;;
   ```

3. **Collector Extensibility (`bin/omarchy-agent-usage-update`)**
   Currently, `omarchy-agent-usage-update` strictly iterates over `"$OMARCHY_PATH"/bin/omarchy-agent-usage-*`. Allowing it to discover collectors in `$HOME/.local/bin/omarchy-agent-usage-*` as well would enable both Antigravity and community agent collectors to work out-of-the-box without modifying system packages.

4. **Quickshell Menu (`default/omarchy/omarchy-menu.jsonc`)**
   Add the agent menu entry:
   ```jsonc
   "setup.default.agent.agy": {
     "icon": "󰚩",
     "label": "Antigravity",
     "checked": "[[ \"$(omarchy-default-agent)\" == \"agy\" ]]",
     "action": "omarchy-default-agent agy"
   }
   ```

5. **Bar Widget Assets (`shell/plugins/agents/assets/`)**
   Add `antigravity.svg` and `antigravity-light.svg` to support panel branding and high-contrast surfaces.

---

### System Details

- **Omarchy Version:** 4.0.4-1
- **OS:** Arch Linux (x86_64)
- **Compositor:** Hyprland
- **CLI Binary:** `agy` (installed via `mise`)