Clear the 'on you' panel in one go: select many, decide together, undo for ten seconds #10780

Intent: the owner's panel is full and clearing it one by one is the problem.

• [ ] Each row has a checkbox; 'select all shown' respects the current filter; a bar offers the decisions that apply to every selected row (decline, snooze, approve where safe).
• [ ] The decision is applied in one request, receipted, and the page keeps its place; an Undo for ten seconds reverts the whole batch.
• [ ] Same action as an MCP action on an existing tool; bun test test/mcp-size.test.ts passes.
• [ ] Tests: batch applies, partial failure names the failures, undo restores, same-origin check holds.

Files: the on-you page under src/web/pages, src/actions/*, test/on-you-bulk.test.ts. Risk: one wrong tap on many; only reversible decisions are offered in bulk. Brief: scout.

Done on main already, waiting for you to close it: e3a5214155737b7315e19330306cb90c44b00ba8

Closed: already done on main in e3a5214. Closed by the crew's live triage; reopen it to undo, and it stays open.