hermes - 💡(How to fix) Fix feat: /dashboard slash command to list agent dashboard URLs [1 pull requests]

Problem

Each Hermes agent host serves its own hermes dashboard on :9119 (hermes_cli/_parser.py:73). Users on a multi-host setup (Tailscale fleet) have no shortcut from inside Hermes (CLI or Telegram) to reach the dashboards on sibling hosts — they have to remember each host's URL.

Proposed design

Add a /dashboard slash command driven by config:

# ~/.hermes/config.yaml
dashboard:
  agent_hosts:
    - {name: emma, url: http://emma.tailnet:9119}
    - {name: ann,  url: http://ann.tailnet:9119}

• New CommandDef("dashboard", ...) in hermes_cli/commands.py.
• CLI handler in cli.py: prints the list as plain text.
• Gateway handler in gateway/run.py: on Telegram emits an InlineKeyboardMarkup with one URL button per host; other platforms get a Markdown list.
• Empty-state message tells users where to add hosts.

Design context: qike-ms/hive → docs/fleet-orchestration/hermes-hub-spoke-design.md §7 (Agents Dashboard — Stage 2).

Acceptance criteria

• /dashboard registered, available in both CLI and gateway surfaces
• CLI prints name: url lines; empty state is friendly
• Telegram emits inline URL buttons via InlineKeyboardMarkup
• Tests cover keyboard helper + registry membership
• No regressions in existing slash-command tests