A fork's page says in one line how it follows its upstream and an admin switches it in one tap #10748

Intent: the owner sees and controls the follow mode (follow automatically, or only propose) where the fork is, not in a settings maze.

• [x] A fork's repository page shows one plain line: Follows <upstream> automatically or Proposes updates from <upstream>, with the mode's reason beside it.
• [x] An admin sees a single button that switches the mode after a confirm that previews what changes; the switch is a POST with a same-origin check, receipted in the audit log, and has an MCP action with the same words (extend the existing repo tool; add no tool).
• [x] Tests: the page for each mode, the switch refused for a non-admin and for a cross-origin request, the MCP action; bun test test/mcp-size.test.ts passes.
• [x] Read first: reuse the existing follow setting (src/web/pages/upstream-follow.ts, following.ts); if the line already exists, add only what is missing.

Files: src/web/pages/upstream-follow.ts, src/http/mcp/tools/, tests. Risks: switching to automatic must never run without the existing conflict-to-crew path; never raise MCP ceilings. Suggested: scout (fork tree brief).

Reviewed pull #10765 at its head: ticked A fork's repository page shows one plain line: Follows <upstream> automatically or Proposes updates from <upstream>, with the mode's reason beside it.; An admin sees a single button that switches the mode after a confirm that previews what changes; the switch is a POST with a same-origin check, receipted in the audit log, and has an MCP action with the same words (extend the existing repo tool; add no tool).; Tests: the page for each mode, the switch refused for a non-admin and for a cross-origin request, the MCP action; bun test test/mcp-size.test.ts passes.; Read first: reuse the existing follow setting (src/web/pages/upstream-follow.ts, following.ts); if the line already exists, add only what is missing..