The `feed` tool's answer draws a ui://forge/feed card: the latest ten items, each a line and a link #3348

src/web/studio/cards.ts draws cards for apps, now, asks and milestones only. The feed tool answers JSON, so in a harness that shows MCP Apps the front door reads as text.

Done:

• [ ] A feed card kind in CARD_KINDS and CARD_OF_TOOL, titled "Feed". It shows one row per item (who, what, the repository, relative time), up to ten, each linking to its page, with the status line "N new since you last looked" when the tool returns that, and "Latest" otherwise.
• [ ] Only the data the tool already returns is used. Values are escaped as for the other kinds.
• [ ] Tests: ui://forge/feed is listed among the resources, the feed tool's descriptor points at it, and a seeded feed draws its rows. They fail without the change.

Files: src/web/studio/cards.ts, src/http/mcp.ts, a test. Risk: #3343 adds the map kind to the same arrays, so rebase onto whichever lands first. Builder: mason.