docs: media thumbnail as Instagram Reel cover (public API + MCP)

[giladresisi]

Documents the optional thumbnail on post media objects: the path of an uploaded JPEG/PNG used as the video cover, i.e. the Instagram Reel cover.

• public-api/openapi.json: thumbnail on the Media schema
• public-api/providers/instagram.mdx: new "Reel Cover Image" section
• mcp/tools.mdx: attachments may be { path, thumbnail }

Backend: gitroomhq/postiz-app#1855 (Instagram cover_url + MCP { path, thumbnail } attachments). Sibling agent docs: gitroomhq/postiz-agent#18.

Merge only after postiz-app#1855 is deployed.

Verified locally with mint dev (pages render, no overflow) and scripts/check-docs.mjs.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added support for optional video thumbnail URLs, enabling custom cover images for Instagram Reels.
  • Video attachments can now include both a video path and an optional thumbnail path.

• Documentation

  • Updated media schema documentation to describe thumbnail usage.
  • Added guidance for uploading and assigning custom Reel cover images.

[postiz-agent]

✅ Snyk checks have passed. No issues have been found so far.

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✅	Code Security	0	0	0	0	0 issues

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f766beab-0017-46e1-81a3-95a629fa11ae

📥 Commits

Reviewing files that changed from the base of the PR and between ad29a3f and 9682f84.

📒 Files selected for processing (1)

• public-api/providers/instagram.mdx

💤 Files with no reviewable changes (1)

• public-api/providers/instagram.mdx

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📝 Walkthrough

Walkthrough

The change adds optional video thumbnail support to the public media schema and attachment documentation. It also documents custom Instagram Reel cover uploads, thumbnail usage, fallback behavior, and an example media object.

Changes

Instagram Reel thumbnail support

Layer / File(s)	Summary
Media thumbnail contract public-api/openapi.json, mcp/tools.mdx	The Media schema and attachment documentation now define an optional thumbnail URL for video covers.
Instagram Reel cover guidance public-api/providers/instagram.mdx	The provider documentation describes custom JPEG/PNG Reel covers, fallback frame selection, and a video media example.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 9682f

This change documents an optional Instagram Reel cover field across the public API and MCP documentation; no actionable merge-blocking risk remains after normal checks and review.

Possibly related issues

• gitroomhq/postiz-app#1572 — Adds documentation and schema support for using m.thumbnail as the Instagram Reel cover_url.

Possibly related PRs

• gitroomhq/postiz-docs#224 — Updates related media upload and video handling documentation, including thumbnails and covers.

Suggested reviewers: egelhaus

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the documented media thumbnail support for Instagram Reel covers across the public API and MCP.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/ig-reel-cover

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[egelhaus]

LGTM - will merge once app PR is merged