feat: open markdown attachments directly in the desktop document viewer

[jeanfbrito]

Proposed changes (including videos or screenshots)

Markdown attachment title clicks in the desktop app now open the document viewer directly via openDocumentViewer — the same flow PDF attachments already use — instead of relying on the desktop app intercepting will-download events.

The new branch is gated on a new optional desktop capability, supportedDocumentViewerFormats?: () => string[] (declared on IRocketChatDesktop), exposed by the desktop app in RocketChat/Rocket.Chat.Electron#3354. Behavior by environment:

• New desktop + this change: title click opens the markdown viewer directly; the download button is never touched by viewer logic.
• Older desktop (no capability): falls through to the existing anchor navigation, which older desktop builds intercept — current behavior preserved.
• Browser: unchanged (no RocketChatDesktop).
• Encrypted markdown files: unchanged, keep the existing encrypted download flow.

Why

The will-download interception in the desktop app cannot reliably distinguish view intent from download intent (see RocketChat/Rocket.Chat.Electron#3345 — download button opened the viewer and the download hung). Opening the viewer through the desktop API removes the viewer from the download path entirely.

Related

• Can't download markdown files Rocket.Chat.Electron#3345
• Fix: markdown download cancellation logic Rocket.Chat.Electron#3348 (transitional desktop-side guard)
• feat: expose supportedDocumentViewerFormats on the desktop API Rocket.Chat.Electron#3354 (desktop capability)

[dionisio-bot]

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[changeset-bot]

🦋 Changeset detected

Latest commit: 73d4db9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@rocket.chat/desktop-api	Minor
@rocket.chat/meteor	Patch
@rocket.chat/core-typings	Patch
@rocket.chat/rest-typings	Patch

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[codecov]

Codecov Report

❌ Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.04%. Comparing base (a6bebd2) to head (73d4db9).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #40915      +/-   ##
===========================================
- Coverage    70.04%   70.04%   -0.01%     
===========================================
  Files         3355     3355              
  Lines       129162   129172      +10     
  Branches     22372    22350      -22     
===========================================
+ Hits         90474    90475       +1     
- Misses       35396    35402       +6     
- Partials      3292     3295       +3     

Flag	Coverage Δ
unit	69.92% <10.00%> (-0.02%)	⬇️

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