✨ Tiger Documentation - Document the end-of-meeting trigger and surface it in notifications

[suiyangqiu]

Pain

Users are confused about how to correctly trigger SSW.Tiger at the end of a meeting (whether they need to stop the meeting, stop the recording, or leave). Tiger is post-meeting and reactive - it has no "meeting start" hook - so the realistic fix now is clear documentation plus surfacing the trigger steps through the Teams messages users already receive. The true in-meeting "Tiger is active" message at meeting start is tracked separately in #128 (blocked on the custom Teams bot).

Split out from #119.

Acceptance Criteria

1. A short Tiger documentation page exists explaining: that Tiger monitors qualifying meetings, the exact action needed to get a summary (make sure recording is on, then stop recording or end the meeting), that you do NOT need to leave the meeting, and who receives the summary.
2. The trigger explanation is accurate to actual behaviour: Tiger fires when Microsoft Graph finalizes the transcript (recording/transcription stops or the meeting ends), not when a participant leaves.
3. The docs page states correctly who receives the summary (see open decision below).
4. The existing started and completed Teams DM notifications include a one-line "How Tiger works" footer linking to the docs page.
5. Wording is short, unambiguous, and suitable for non-technical users.

Open decision (blocks the wording)

Today Tiger DMs all participants (organizer + attendees), not only the recorder, despite the original AC #4 on #119. Decide before writing copy: keep current behaviour and word it "all participants receive the summary", or change recipient logic to recorder-only so "only the recorder" becomes true. Also: docs page location - repo docs/ vs sswtiger.com.

Out of scope

A message shown at the moment the meeting starts. Not possible without a meeting-scoped bot. Tracked in #128.