feat(mcp): add content_upload_media tool for image uploads

[hectorcanaimero]

What

Adds content_upload_media, a server-resolved MCP tool that uploads an image into the Media library and returns its id + publicPath.

Why

The MCP surface could list and assign media but never create it — an external agent building a page had no way to get an image into the library. This closes that gap.

How

• Bytes arrive inline (base64, data: URI prefix tolerated) or via an https sourceUrl the host downloads.
• The sourceUrl branch is SSRF-guarded exactly like the plugin network layer: https-only, DNS-resolved, every resolved address checked against the shared isBlockedAddress blocklist, redirects followed manually and re-validated per hop, and the download size-capped while streaming. Loopback / private / link-local (incl. 169.254.169.254) targets are refused.
• Reuses the existing acceptUploadedMedia core — magic-byte MIME sniffing, SVG sanitisation, storage dispatch, responsive variants. No new byte-handling path is introduced.
• Hoists the 50MB ceiling to MAX_MEDIA_BYTES in the upload core so the HTTP media route and the tool share one source of truth.
• Gated by ai.tools.write + media.write, following the site_publish server-tool precedent.

Impact

• Connectors/agents: can now upload images (JPEG/PNG/GIF/WebP/SVG) headlessly, without an open editor.
• No schema changes, no migrations, no changes to existing tool behaviour. content_list_media's description was corrected (it claimed uploads were impossible).

Verification

• bun test server/ai/mcp/tools/uploadMediaTool.test.ts server/ai/mcp/registry.test.ts — 11/11 pass, including SSRF-blocklist rejection cases (127.0.0.1, 169.254.169.254, 10.x, ::1), non-https rejection, source XOR, and non-image rejection.
• Typecheck clean on the touched files.
• bun run build / bun run lint left to CI (dev toolchain not available in the author's environment).

Docs updated: docs/features/mcp-connectors.md.

[DavidBabinec]

Thanks, this is useful. There are two changes needed before merge.

First, the build is currently failing with:

server/ai/mcp/tools/uploadMediaTool.ts(190,28): error TS2322: Type 'Uint8Array<ArrayBufferLike>' is not assignable to type 'BlobPart'.
  Type 'Uint8Array<ArrayBufferLike>' is not assignable to type 'ArrayBufferView<ArrayBuffer>'.
    Types of property 'buffer' are incompatible.
      Type 'ArrayBufferLike' is not assignable to type 'ArrayBuffer'.
        Property 'resize' is missing in type 'SharedArrayBuffer' but required in type 'ArrayBuffer'.
Error: Process completed with exit code 2.

Second, please rename the new MCP tool from content_upload_media to media_upload throughout the implementation, tests, descriptions, and docs. In Instatic, the content_* namespace refers specifically to the Content editor for posts and other structured content, while Media is its own product area and is also consumed by the Site editor.

We’ll handle content_list_media → media_list and add the rest of the media-related MCP tools in a separate follow-up PR. This PR should establish the new media_* namespace with media_upload.

[hectorcanaimero]

Thanks for the review — both addressed in a56a66b.

Build fix: the decoded/downloaded bytes are now typed Uint8Array<ArrayBuffer> at their source functions, so the File constructor accepts them without a cast. tsc -b is clean locally now (that was TS2322 on the BlobPart assignment).

Rename: content_upload_media → media_upload throughout — implementation, tests, descriptions, and docs/features/mcp-connectors.md — establishing the media_* namespace. Left content_list_media untouched for your follow-up PR. The stale 'to add a new image, use …' hint in its description now points at media_upload.

Verified in the oven/bun:1.3.11 toolchain: tsc -b exit 0, and bun test on the upload + registry suites is 11/11 (including the SSRF-blocklist rejection cases).