* fix(telegram): preserve unsent media while deduplicating streamed replies
## What Problem This Solves
A Telegram final reply could resend an attachment already delivered in a streamed block when the legacy mediaUrl still referenced that sent attachment while another mediaUrls item remained. Conversely, unsent legacy-only attachments must not be discarded.
## Why This Change Was Made
The Telegram media-deduplication owner now clears mediaUrl only when its normalized attachment was actually sent, preserving independently unsent legacy attachments and preventing downstream outbound planning from restoring delivered media.
## User Impact
Telegram replies retain every unsent attachment exactly once and no longer duplicate already streamed images in mixed final-message payloads.
## Context
Seven zero-dependency scenarios passed against the actual media owner and outbound planner, including mixed legacy/vector attachments, whitespace normalization, visible-send handling, and remaining-media preservation. The exact frozen campaign baseline passed 844 tests. Existing oxfmt formatting and staged whitespace checks passed; focused Vitest CI remains pending.
* refactor(telegram): inline legacy media dedup check
* fix(telegram): suppress message-tool-only reply fallbacks
Honor message-tool-only delivery when a non-silent Telegram reply is skipped in both ordinary group dispatch and native slash-command turns. Keep the existing visible fallback for genuinely empty native replies and cover both dispatch surfaces with regression tests.
Fixes#90091
* fix(telegram): preserve genuine delivery failure fallbacks
Suppress only non-silent skips owned by message-tool-only delivery. Preserve visible fallbacks when the same turn also encounters a real dispatch or final-delivery failure, with an explicit regression for the mixed failure path.
* fix(telegram): preserve native message-tool delivery errors
Track genuine native slash delivery failures so message-tool-only skip suppression never hides a failed response. Cover the exact mixed empty-skip and real-error path with a regression while preserving true-empty and intentionally cancelled fallbacks.
* test(telegram): preserve synchronous native delivery callbacks
Peter Steinberger