What does this PR do?

Adds a send_document fallback to the Telegram adapter's send_image_file when Telegram rejects the photo.

Telegram rejects photos with extreme aspect ratios (most commonly very tall full-page screenshots) with Photo_invalid_dimensions. Previously the adapter logged the error and called super().send_image_file(...), which on the Telegram path silently dropped the file — the user got nothing.

This PR retries the same bytes via send_document when send_photo raises, so the original image still reaches the user (just as a file rather than an inline preview). Only fall through to the base adapter if both attempts fail.

This complements #17833 (which added a similar send_voice → send_document fallback for unplayable audio formats), but for the image path.

Related Issue

No existing issue — observed in the wild while sending agent-rendered web-page screenshots over Telegram.

Type of Change

• ✨ New feature (non-breaking change that adds functionality)

Changes Made

• gateway/platforms/telegram.py — send_image_file():
  • On send_photo exception: log a warning (was error) noting we're retrying as a document.
  • Retry via self.send_document(...) with the same bytes / caption / metadata.
  • If send_document also raises, log a final error and fall through to the base adapter (existing behaviour).
• tests/gateway/test_send_image_file.py — add a case asserting the document fallback is invoked when send_photo raises BadRequest.

How to Test

1. Generate an extremely tall PNG (e.g. a full-page web screenshot via the browser skill).
2. Tell the agent to send it via Telegram with a chat session that produces an image attachment.
3. Before this fix: Telegram fails with Photo_invalid_dimensions; nothing arrives in the chat.
4. After this fix: the image arrives as a Telegram document, with the same caption preserved.

Or run the unit tests:

pytest tests/gateway/test_send_image_file.py -v

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (feat(telegram): ...)
• I searched for existing PRs to make sure this isn't a duplicate (feat(gateway): centralize audio routing + FLAC support + Telegram doc fallback #17833 covers send_voice, not send_image_file)
• My PR contains only changes related to this feature
• I've run pytest tests/ -q and the changes don't introduce new failures (vs. main baseline)
• I've added tests for the change
• I've tested on my platform: macOS 15 (Apple Silicon)

Documentation & Housekeeping

• No public API surface changed
• No config schema changed