feat(comms): peer-DM T0 name-addressing cutover — agents address channels+topics by name (RIG-2956)

[rigel-mintaka]

The T0 slice of the peer-DM name-addressing cutover (frozen record
docs/designs/product/compass-agent-peer-dm/design.md §T0). Agents and UIs
address channels and topics by NAME; the wire and store stay id-typed,
resolved at the service edge (mirrors the merged handle-addressing cutover
#698 / DL-270). Proto denorm fields + Go edge + delivery denorm + TS tools,
one atomic change.

Proto (regen committed):

• DeliverControl.channel_name=5, SteerControl.topic_name=4/channel_name=5:
  the source channel/topic NAMES ride the deliver/steer control op so the
  agent renders them without a roster lookup.
• PostMessageRequest.create_topic=6: the get-or-create gate (R5).

Go comms edge:

• store.ChannelByNameForViewer: viewer-scoped name→id resolve, sharing
  channelVisiblePredicate with ListChannels (no read/resolve drift).
  Unknown OR invisible name → ErrNotFound (D9 merge); ambiguous name →
  ErrInvalidArgument naming the collision (no ErrAmbiguous sentinel).
• TopicRef.Create gates get-or-create in resolveTopicForAppend: set → mint;
  unset → a name-miss is ErrNotFound, not a silent create (R5). Archived
  revival unchanged.
• comms_post_message / comms_post_ask route through the new
  PostAsAccountByName / ListAsAccountByName tool-arm wrappers, which resolve
  the channel NAME → id then delegate to the UNCHANGED id-typed
  PostAsAccount / ListAsAccount. Post/ask drop the home default (R2 — the
  agent must name its channel, even its own home); list keeps omit-=home
  (a read has no misroute hazard).
• defaultChannel: preserve CreateTopic on its home-channel request copy
  (latent bug the create_topic gate would have surfaced as a silent
  mint-failure on CommitAgentPost's frame-relay path).
• Internal producers that legitimately mint set Create=true (serve_seed
  Setup seed, CommitAgentPost frame relay, test helpers).

Go delivery denorm:

• store.TopicChannelNames(topicID) → (topicName, channelName): id-typed
  join, ErrNotFound on miss.
• Consumer.sourceNames mirrors authorHandle (empty topic id → empty; store
  miss → log + empty, never blocks delivery); deliverOp/steerOp carry
  ChannelName+TopicName on both DeliverControl and SteerControl.

TS agent tools:

• comms_post_message / comms_post_ask require an explicit channel NAME
  (home default dropped) + optional create_topic; comms_list_messages flips
  to a channel NAME param, keeps omit-=home. The name rides the existing
  container channelId arm (the Go edge resolves).
• formatDeliversForPrompt renders "Channel › topic :" + a reply
  cue naming both required post params; source names plumbed per message via
  #deliverSourceNames, mirroring #deliverFromHandles. Resolve misses degrade
  (topic → id, channel → placeholder).

Spec-impact: none. The name-addressing invariant (agents/UIs address by name; wire + store stay id-typed) is already recorded in the frozen design record and DL-291..297; this is its T0 implementation.

Refs RIG-2956

Co-authored-by: Matt Wilkinson matt@rigel.build

[linear-code]

RIG-2956

[github-actions]

Compass engineering docs preview: https://compass-rig-2956-t0-name-add.compass-eng-docs.pages.dev

Deployed from compass/rig-2956-t0-name-addressing at 076b877.