Declare MCP output schemas as objects

Wrap the rename, archive and restore result unions in object schemas without changing their branches. Check every exported tool and the fully enabled MCP tools/list response.

Assistant-model: Claude Opus 5.5
Assistant-workflow: goal (run 98acf681-3730-4957-b885-0d70e0e6b32a)
Assistant-verification: focused MCP tests passed: 81 tests, 450 assertions; the new invariant failed before the fix on rename_document
Assistant-verification: bun run types passed: all workspaces and E2E
Assistant-verification: bun run fix and bun run ci passed: formatting inspected, no errors and one existing lint warning
User-preference: "Atomic's SDK is the runtime and the host supplies human input; Chopin implements HostInput rather than intercepting tools"
User-preference: "In local mode the Planner may run as a full Atomic session so workflows run inside Chopin with questions in Decisions"
Co-authored-by: Alex Lavaee <lavaman131@github.com>