mirrordaemon: drop dead debug peersKnown api parameter

[ToadAid]

Description:

• remove the dead peersKnown parameter from the mirrordaemon debug API
• remove the matching dead peersKnown override from the debug snapshot builder
• preserve debug response shape, field names, status codes, and all runtime/boot/session/diagnostic/recent-event data
• keep scope limited to debug_api and runtime_state
• verification passed:
  • pnpm check
  • pnpm vitest run src/mirrordaemon/mirrordaemon.test.ts src/mirrordaemon/runtime_state.test.ts