notify: add pre_formatted flag for HTML pass-through

[bermudas]

Summary

• Adds optional pre_formatted: bool parameter to send_notification() in scripts/notify_lib.py (default False — preserves existing safe-escape behavior for every current caller, including supervisor.py's stuck-role warnings).
• Exposes the same flag on the notify MCP tool in mcp/notify/server.py with default True so agents calling the tool can emit Telegram HTML (<b>, <i>, <code>, <a href>) without their markup being escaped to literal <b> text in the chat.
• The role badge prefix is always HTML-escaped regardless of the flag — only the message body is affected.

Ported from ChildrenHomeWork/octobots. Asymmetric defaults are intentional: only MCP callers (agents) opt into HTML pass-through; other Python callers keep the safe default.

Trade-off worth flagging

With MCP default True, an agent that emits e.g. notify("found <UserService> bug") will fail the Telegram API call because <UserService> looks like an unclosed tag. The pre-existing fallback path doesn't catch HTML parse errors, so the call returns an error dict — visible to the agent but not silently swallowed. Discuss whether to keep MCP default True or flip it to False and have agents opt in per-call.

Test plan

• notify(message="<b>done</b>") from an agent renders bold in Telegram
• notify(message="plain text & special chars", pre_formatted=False) renders literally
• send_notification("text with <angle>") from supervisor.py (no flag) still escapes safely