#21309: feat(telegram): support outbound media groups (albums) via sendMediaGroup

## Summary - When a reply contains 2–10 media items that are **all photos or videos** (no gifs, audio, or documents), send them as a Telegram album via `bot.api.sendMediaGroup()` instead of individual `sendPhoto`/`sendVideo` calls - Only the first item carries the caption (Telegram displays it as the shared album caption) - Mixed media (containing gifs, audio, or documents) falls back to the existing single-item send path — zero behavior change for non-groupable content - When caption exceeds Telegram's 1024-char limit, the overflow text is sent as a follow-up message (reuses existing `splitTelegramCaption` logic) - Inline buttons are sent as a follow-up message since `sendMediaGroup` does not support `reply_markup` ## Motivation Closes #13620 Closes #14027 Currently the outbound path always sends media one at a time, even when the agent produces multiple images in a single response (e.g. image generation tools). Telegram's `sendMediaGroup` API groups 2–10 photos/videos into a single album message, which is much cleaner for the end user. Note: OpenClaw already handles **inbound** media groups correctly (via `mediaGroupBuffer` in `bot-handlers.ts`). This PR fills the outbound gap. ## Changes - `src/telegram/bot/delivery.ts`: Add media-group detection and `sendMediaGroup` call path before the existing single-item loop; import `InputMediaBuilder` from grammY - `src/telegram/bot/delivery.test.ts`: Add 5 test cases covering album send, mixed photo+video, gif fallback, audio fallback, and single-image non-grouping; update grammY mock to include `InputMediaBuilder` ## Commits - `1c4036e` feat(telegram): support outbound media groups (albums) via sendMediaGroup ## Validation ``` pnpm vitest src/telegram/bot/delivery.test.ts ``` 16 tests pass (5 new + 11 existing). <!-- greptile_comment --> <h3>Greptile Summary</h3> Adds Telegram media group (album) support for outbound messages containing 2-10 photos/videos. When all media items are groupable (photos or videos, no gifs/audio/documents), they're sent via `sendMediaGroup` as a single album instead of individual messages. The implementation correctly falls back to single-item sends for mixed content, handles caption overflow via follow-up messages, and sends inline buttons separately since `sendMediaGroup` doesn't support `reply_markup`. - Introduces media groupability check before attempting album send (photos and videos only, no gifs) - Reuses existing `splitTelegramCaption` logic for handling 1024-char caption limits - Comprehensive test coverage including album sends, mixed photo/video, and fallback scenarios for gifs and audio - Clean integration with existing single-item send path as fallback <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The implementation is well-designed with comprehensive test coverage (5 new tests covering all major code paths), clean fallback behavior, and proper integration with existing caption/button handling logic. The code correctly handles edge cases (gifs, audio, single media), reuses proven utilities, and maintains backward compatibility by falling back to the existing single-item send path for non-groupable content. - No files require special attention _{Last reviewed commit: 1c4036e} <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->