feat(store): unique sibling channel-group names with a repairing migration (RIG-3030)

[rigel-mintaka]

Summary

Channel-group names cannot contain /. A top-level name is unique per namespace, and a nested name is unique under its parent. So a slash path from main's group-ref resolver (#1705) names at most one group under a given parent.

• Migration 0002_channel_group_names.sql repairs existing rows as compass_system:
  • slash names are rewritten;
  • duplicates get a free -N suffix, and the pre-existing valid name is kept;
  • reserved top-level groups are untouched.
• It then adds a partial unique index on (namespace for top-level groups, parent, name) and a no-slash CHECK.
• CreateChannelGroup maps the unique violation to AlreadyExists.

History

This PR was re-sliced onto main. #1705 (RIG-4344) shipped agent group refs by leaf or slash path, which superseded this PR's resolver half (ChannelGroupByNameForViewer, pickGroup, the group_id-as-name agent wiring). Only the constraint half remains, as one commit.

Testing

• Migration pgtest: duplicates, suffix skip, slash rewrite and collision, reserved names, nested, cross-tenant.
• TestCreateChannelGroupSiblingNamesUnique, TestCreateChannelGroupNestedNameUniquePerParent.
• Full store pgtest suite: ok, no skips.
• sqlc-vet, the migration gate, the proto gates and golangci-lint all pass.

Linear: RIG-3030

RIG-4458 (ruled A + K1)

• K1: a new namespace_owner_id column (the agent's owner user) keys the sibling-name index. A trigger fills it for inserts that omit it, so older binaries keep working during a rolling deploy.
• A: a leading / anchors a ref at top level, and /~handle/ qualifies the top-level owner. An ambiguous ref still returns invalid_argument (DL-291), and the error names a ref for each match.
• Visibility: an OWNER group an agent creates is now visible to its user and to that user's other agents, as the proto says.
• Review: Opus found 3 medium and 4 low. All are fixed. The nested shared-parent dead end went to RIG-4651.
• The migration is 0002_channel_group_names.sql on the collapsed baseline.

RIG-4651 (ruled)

• A shared group has no per-user namespaces, so pub/infra exists once. A second create of the same name returns AlreadyExists.
• The sibling index keys nested groups on the parent alone. Top-level names stay per namespace (K1).
• The migration repair suffixes duplicate nested siblings across namespaces. The spec gains a scenario for this.

Ledger-impact: none (implements the RIG-4458 and RIG-4651 rulings in the record's own terms; no DL row changes).

[linear-code]

RIG-3030

[github-actions]

Compass engineering docs preview: https://compass-server-rig-3030-grou.compass-eng-docs.pages.dev

Deployed from compass-server/rig-3030-group-refs-by-name at ae8ae97.

Changed pages:

• docs/specs/product/compass.md

[trunk-io]

❌ This pull request could not start testing because there was a merge conflict. See more details here.

• To merge this pull request, check the box to the left or comment /trunk merge below.

After your PR is submitted to the merge queue, this comment will be automatically updated with its status. If the PR fails, failure details will also be posted here