feat(ai): name agents after their model, not hardcoded "oracle"

Agents now join under their model tag (e.g. "qwen2.5:3b" — model name +
parameter size) or profile label, derived at /ai start and tracked on
App.agent_name, so the roster shows what's actually answering. Updates the
broker re-grant + /ai stop revoke paths, the Python --name default
(falls back to provider.model), and the demo/bootstrap/README/docs refs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hh/src/ui.rs

@@ -567,7 +567,8 @@ fn draw_roster(f: &mut Frame, area: ratatui::layout::Rect, app: &App, theme: &Th
     f.render_widget(roster, area);
 }
 
-/// Animated "⠋ oracle is thinking…" title shown while AI agents generate a reply.
+/// Animated "⠋ <agent> is thinking…" title shown while AI agents generate a
+/// reply. The name(s) come from `app.ai_typing`, i.e. each agent's own handle.
 fn ai_thinking_title(app: &App) -> String {
     const FRAMES: [&str; 10] = ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"];
     let glyph = FRAMES[(app.spin / 2) % FRAMES.len()];