Summary

• derive Telegram no-caption inbound media placeholders from saved media MIME metadata instead of the Telegram photo message shape
• keep multiple image placeholders as image summaries, and mixed/non-image saved media as document/attachment placeholders
• add regression coverage for issue Bug: Telegram photo inbound always sets bodyText=<media:image> regardless of actual contentType #69793 and changelog credit

Fixes #69793

Verification

• repro before fix: pnpm test:serial extensions/telegram/src/bot-message-context.body.test.ts -- --reporter=verbose failed 3 new cases with <media:image> returned for non-image/mixed saved media
• pnpm test:serial extensions/telegram/src/bot-message-context.body.test.ts -- --reporter=verbose passed 9 tests
• pnpm exec oxfmt --check --threads=1 extensions/telegram/src/bot-message-context.body.ts extensions/telegram/src/bot-message-context.body.test.ts
• git diff --check
• OPENCLAW_TESTBOX=1 pnpm testbox:run --id tbx_01kqtnnhpg6rk1225tbb7109kf -- "pnpm check:changed" passed

Notes

• ghx was not on PATH, so GitHub operations used gh.
• AI-assisted: yes.