docs(compass): design collapsing the channel-group tree into the agent tree (RIG-2684)

[rigel-mintaka]

Moved

• Moved from docs(agent): design collapsing the channel-group tree into the agent tree (RIG-2684) compass#2170: design records now live in this repo, under docs/designs/compass/.
• Links to compass records that have not moved point at compass main blob URLs.
• The status-line edits to DL-295, DL-395, DL-344 and DL-397 are carried in the second commit. Those records have since moved here.

Summary

Design record for RIG-2684: collapse the channel-group tree into the agent tree, so Compass has one hierarchy. It builds on docs/designs/ui/compass-channels-in-agent-tree (DL-344/345/397), which moved channels into the agent tree but kept ChannelGroup as server machinery. This record removes what is left.

Record: docs/designs/agent/compass-collapse-channel-group-tree/design.md. New rows DL-487 to DL-490, all Active (proposed, pending Matt, 2026-10-11).

Decisions (proposed)

	Decision
D1	Delete channel_groups, channels.group_id, the MIN-over-ancestry lattice, channels_group_name_key and channels_group_xor_agent. DL-345's owner-set grant is the only tree visibility class.
D2	The DM, coordination and Linear homes become channels.system_namespace + namespace_owner_id, unique per owner. ReparentChannel refuses system channels.
D3	SHARED spaces become channels.shared on root channels (channels_shared_root_only), keeping DL-397's "never in a tree".
D4	Agents organize channels through the agent tree: comms_create_channel gains parent?/shared?; comms_create_channel_group goes.
D5	Group wire removed without reserved (DL-186); shared at fresh numbers Channel.shared = 13, CreateChannelRequest.shared = 8. No field number is reused at a new wire type.
D6	Edits 0001_init.sql in place per the pre-wipe policy (RIG-4927). A deployed dev DB needs a recreate; no backfill.
Landing	One atomic implementation PR: a single proto regen removes TS symbols the agent, UI and client import, so no smaller PR is green.

Supersession

• ui/DL-344: clause-level, only "ChannelGroup is NOT deleted" (→ DL-487).
• ui/DL-397: clause-level, only the permanent channels_group_xor_agent CHECK clause (→ DL-488, replaced by channels_shared_root_only). Clause-level statuses follow the DL-097/DL-208 precedent.
• agent/DL-295 and server/DL-395 → DL-489.
• Kept: DL-345, DL-294, DL-296, DL-135, DL-136, DL-190, DL-416.

Open questions for Matt

OQ1–OQ5 are load-bearing and filed as RIG-5154. The Plan builds each recommendation.

Review

An adversarial design critic and two review-correctness rounds; every finding is folded in. Review at head 526d84b3: 0 high, 0 medium, 0 low, 0 nit (see the PR comment).

Spec-impact: none
Ledger-impact: DL-487..490 added (proposed); DL-344 and DL-397 clause-level, DL-295 and DL-395 flipped to superseded (proposed)

Refs RIG-2684

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

[linear-code]

RIG-2684

[github-actions]

Rigel public design docs preview: https://compass-comms-rig-2684-colla.docs-2ui.pages.dev

Deployed from compass-comms/rig-2684-collapse-group-tree-design at 9732f85.

[rigel-mintaka]

Head note at 9732f85ea4592d368a3f7f1ab20fd6c36028e263 (base main b752ded3).

• Rebased onto main with no conflicts. The record matches the review at compass#2170 526d84b3: 0 high, 0 medium, 0 low.
• 9732f85e carries the deferred status lines for DL-295, DL-395, DL-344 and DL-397, which now live here. A delta review found 0 findings, and the design-ledger gate passes.
• Local: rumdl, biome, the design-ledger gate and ref-gate are clean. CI check is green.
• OQ1-OQ5 are still open for Matt in RIG-5154.