Phase 2.6: Publication/subscription visibility

[aesslinger]

Part of the Phase 2 set of PostgreSQL-specific features beyond the built-in driver.

Problem

Logical replication (publications and subscriptions) has no visibility in Tabularis. Anyone monitoring or debugging a replication setup — checking whether a subscription is enabled, which tables a publication includes — currently has to query pg_publication/pg_subscription by hand.

Proposed approach

-- Publications
SELECT pubname, puballtables, pubinsert, pubupdate, pubdelete
FROM pg_publication;

-- Subscription status
SELECT subname, subenabled, subslotname, subpublications
FROM pg_subscription;

Frontend integration

New sidebar section, "Replication," listing Publications and Subscriptions as separate sub-nodes.

Acceptance criteria

• Publications list with their table-inclusion flags (puballtables, insert/update/delete)
• Subscriptions list with enabled/disabled status and slot name
• No regressions in existing Phase 1 parity tests

References

• Full spec: docs/planning/03-phase-2-issue-16.md (2.6)
• Priority: Sprint 6 — lower priority, quick win