MCP `apps` takes `archived: true` and lists the apps put away, as /apps?archived=1 does #6083

Today apps (src/http/mcp/tools/apps.ts) reads through appsOf, which drops archived repositories, so an agent cannot find an app the owner archived.

Done when:

• [ ] apps accepts { archived?: boolean }. With true it lists only the archived apps the caller can see, each row carrying archivedAt. Without it the answer is the same as today's.
• [ ] Any other type for archived is refused with a 400-style tool error.
• [ ] A test archives one of two apps, finds it missing from apps and present in apps {archived: true}, and checks a stranger sees neither for a private one.
• [ ] docs/MCP.md names the argument.

Parked by the steward, 2026-10-26 (owner: "get us unclogged now then resume everything else"). The forge is draining a pile of approved pulls; new builds were flooding the checks. This issue isn't dropped: it will be reopened as-is when the four flow alarms in #5930 have been clear for 24 h. The list is kept in the steward's parked-2026-10-26 file.