Phase N channel roster, addressing, and personalities

[alexfrmn]

Summary

• add Phase N channel roster primitives in @murmurv2/core with typed channels, members, addressing decisions, and N3 thread-start binding projection
• expose MCP roster tools for create/list/members/evaluate_addressing
• wire Codex app-server thread/start personality/model/baseInstructions binding behind channelRoster.enabled / MURMUR_CHANNEL_ROSTER=1 (default OFF)
• harden trust boundary: remote payload threadStartBinding is ignored; bindings come only from local peer config or local ChannelRosterStore resolver

Operational Safety

• default behavior remains legacy-safe: buildThreadStartParams() keeps model/personality/baseInstructions null
• daemon creates ChannelRosterStore/resolver only when the channel roster flag is enabled
• no shared NATS restart, no prod deploy, no daemon restart in this PR
• production activation is intentionally gated until after merge and a coordinated deploy window

Verification

• npm run build
• node --test tests/codex-app-server-wake.test.mjs -> 14/14 PASS
• npm run test:unit -> 84/84 PASS
• npm run test:core -> 49/49 PASS
• git diff --check

Review Notes

Jarvis reviewed the N1/N2/N6/N3-code path over Murmur and marked N3 live wiring ship-ready behind the flag. Requested legacy nulled-default regression test is included.