0570 — Topic truth stays on the topic row; history is an append-only log (topic_log, binding_log)

Context. [0519] was built: truth in append-only declaration rows, topic as identity only. The code showed the cost — newest-row lateral joins in every reader across five domains, procedural (name, schema_version) uniqueness with advisory locks on every name write, a lock-plus-re-read on the found-path append. A single-table variant (per-row id plus a stable topic id in one append-only table) was evaluated and rejected: a repeating stable id cannot be a foreign-key target, so consumer_group/worker/cron_job/migration_log lose their FKs and cascades, while every newest-row read and procedural lock remains. The house already holds the working shape: binding [0511] — the current table is the enforced truth, an append-only trail is written in the same transaction, and machinery never reads the trail.

Decision.

• topic keeps the full current-state row: identity, name, partition_size, the mutable config columns, UNIQUE (name, schema_version). Reads stay plain column reads; rename stays one UPDATE with ErrTopicNameTaken from 23505; register keeps its per-name advisory lock for the create race only.
• topic_log is the append-only history: a full snapshot (name, partition_size, config fields, declared_by = common.ProcessIdentity, declared_at), one row appended in the SAME transaction as every create, config replace, and rename (one row per schema_version on rename). Machinery never reads it; it exists for operators to query.
• updated_at stays on the topic row: cheap current-state display, while the log carries the full change history.
• _log is the established suffix for append-only event history (message_log, delivery_log, migration_log — the last even machinery-read). binding_declaration renames to binding_log, its index to binding_log_group, and the Go surface follows. Declare* verbs and declared_by/declared_at columns stay: declaring is the action, the log records it.
• The parked failure-evidence table renames to worker_run_log; worker_log is reserved for worker metadata history when it takes this same shape.

Consequences. Supersedes [0519]; its build was rolled back before ever being committed. Config history stays queryable — when a value changed and which process declared it — without a second read path: the log is display-only data, the same answer [0511] gave to “one fact, two homes”. Rejected: the single append-only table with a stable id (FK hole, keeps every rough edge; an anchor-row self-reference restores FKs but adds a subtler invariant and simplifies nothing); an is_current marker with a partial unique index (writes the prior row — [0519]‘s own rejection stands).