Interactive Button-based Telegram Session Resume UI Improvements

[indigokarasu]

Summary

Replaces the plain-text /resume list on Telegram with an inline keyboard showing the last 12 non-cron named sessions sorted by recency.

Changes

• gateway/platforms/telegram.py: Intercept /resume with no args in _handle_command, send inline keyboard via new _send_resume_button_ui() method. Handle rs:<session_id> callback to dispatch synthetic /resume event.
• gateway/run.py: New get_resume_sessions() method returns structured session data. Fetches from all platforms, excludes cron/tool, filters for titled sessions, stops at 12.
• tests/gateway/test_telegram_resume_button_ui.py: 13 new tests covering interception, button UI, callback handling, auth, and session listing.

UX

• Numbered list (1-12) in message body with title + preview
• Matching numbered buttons (truncated to fit mobile ~40 chars)
• Plain text (no parse mode) — avoids Telegram HTML/Markdown escaping issues with session titles
• Sessions sorted by most recent activity
• Fallback: /resume or /resume still works through normal gateway handling
• Link previews disabled on resume UI messages

Test Results

• 13 new tests: all passing ✅
• 2635 existing gateway tests: 2635 passing, 1 pre-existing failure (MS Graph webhook trio test, unrelated)

[alt-glitch]

This appears to be a resubmission of #33702 (closed, same title and approach — Telegram resume inline keyboard). The prior PR was closed because it included unrelated scope creep (cron retry logic). This version appears scoped to the resume UI only.