A test pins MCP `feed_chips`: switching a chip off hides it from `feed` and `asks`, and bad input changes nothing #7063

The MCP tool feed_chips (src/http/mcp/tools/feed_chips.ts) has no test of its own; only the tool list names it.

Done:

• [ ] A new test calls the tool through /mcp. With no kind, it lists the caller's switched-off chips. { kind: "kind", value, hidden: true } switches a kind off, and the caller's feed and asks tools leave those items out. hidden: false brings them back.
• [ ] { kind: "person", value: <username> } hides that person's items. An unknown name or an org answers not_found.
• [ ] A missing or non-boolean hidden, or a kind with no chip, answers invalid, and nothing is stored.
• [ ] One person's chips never change another's feed.

Files: test/mcp-feed-chips.test.ts

If the test finds the behaviour wrong, fix the tool in the same pull and say so.

If the check fails in a test this pull does not touch, name it in the pull rather than widening the change.

Before pushing: bun x tsc --noEmit and the tests this names.