A repository's JSON carries its visibility line, and the MCP `here` tool repeats it #10433

One sentence: the plain line about who can see a repository (shipped in #10394 for the pages) reaches an agent in the same words.

Done:

• [ ] GET /api/v1/repos/:owner/:name carries visibility: {who: owner | members | signed-in | anyone, why: one sentence}, computed by whoOf in src/core/audience.ts, the same sentence the page shows.
• [ ] The MCP here tool returns the same field when the page is a repository or app; add it to the existing tool's answer, not a new tool.
• [ ] A stranger asking for a private repository gets the same 404 as a missing one (no field leaks).
• [ ] test/visibility-line.test.ts gains a case per audience (owner, member, signed-in, anyone) reading the JSON and the here answer; it fails without the change.
• [ ] bun test test/mcp-size.test.ts passes; the ceilings are not raised.

Files: src/http/api.ts or the repository JSON module it uses, src/http/mcp/tools/here.ts, src/apps/here.ts, test/visibility-line.test.ts Risks: the repository JSON shape is public; add the field, rename nothing. Avoid editing scripts/gate.ts unless the test file is new. Suggested: mason (wrote #10394).

Done on main already, waiting for you to close it: 39198ef9693387197290b8dfd131cf5100438bd0 bc8faa2186148b4193b916e948b20a9557837e77

Closed: already done on main in 39198ef, bc8faa2. Closed by the crew's live triage; reopen it to undo, and it stays open.