iMessage: promote BlueBubbles and refresh docs/skills (#8415)

* feat: Make BlueBubbles the primary iMessage integration

- Remove old imsg skill (skills/imsg/SKILL.md)
- Create new BlueBubbles skill (skills/bluebubbles/SKILL.md) with message tool examples
- Add keep-alive script documentation for VM/headless setups to docs/channels/bluebubbles.md
  - AppleScript that pokes Messages.app every 5 minutes
  - LaunchAgent configuration for automatic execution
  - Prevents Messages.app from going idle in VM environments
- Update all documentation to prioritize BlueBubbles over legacy imsg:
  - Mark imsg channel as legacy throughout docs
  - Update README.md channel lists
  - Update wizard, hubs, pairing, and index docs
  - Update FAQ to recommend BlueBubbles for iMessage
  - Update RPC docs to note imsg as legacy pattern
  - Update Chinese documentation (zh-CN)
- Replace imsg examples with generic macOS skill examples where appropriate

BlueBubbles is now the recommended first-class iMessage integration,
with the legacy imsg integration marked for potential future removal.

* refactor: Update import paths and improve code formatting

- Adjusted import paths in session-status-tool.ts, whatsapp-heartbeat.ts, and heartbeat-runner.ts for consistency.
- Reformatted code for better readability by aligning and grouping related imports and function parameters.
- Enhanced error messages and conditional checks for clarity in heartbeat-runner.ts.

* skills: restore imsg skill and align bluebubbles skill

* docs: update FAQ for clarity and formatting

- Adjusted the formatting of the FAQ section to ensure consistent bullet point alignment.
- No content changes were made, only formatting improvements for better readability.

* style: oxfmt touched files

* fix: preserve BlueBubbles developer reference (#8415) (thanks @tyler6204)

src/channels/plugins/whatsapp-heartbeat.ts

@@ -1,7 +1,7 @@
 import type { OpenClawConfig } from "../../config/config.js";
-import { normalizeChatChannelId } from "../../channels/registry.js";
 import { loadSessionStore, resolveStorePath } from "../../config/sessions.js";
 import { normalizeE164 } from "../../utils.js";
+import { normalizeChatChannelId } from "../registry.js";
 
 type HeartbeatRecipientsResult = { recipients: string[]; source: string };
 type HeartbeatRecipientsOpts = { to?: string; all?: boolean };