A test pins MCP `board_pins`: with no `op` it lists the caller's home pins, and pinning matches the API #7060

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

Done:

• [ ] A new test calls the tool through /mcp. With no op, a person admin gets the same list GET /api/v1/boards/pins gives. Pinning and unpinning a panel through the tool show up in that API.
• [ ] Pinning a panel that does not exist is refused, and the list is unchanged.
• [ ] An agent and a non-admin are refused.

Files: test/mcp-board-pins.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.