0562 — Log events carry VK codes from the error registry

Context

[0550] gave errors stable VK codes with hand-written docs pages; [0558] made logs and errors one message system. The operator-actionable Warn/Error log lines (reclaims, dead-letters, backstops, a stopped tick loop) had no such pointer: an operator grepping a message found nothing stable to search or link.

Decision

• common.NewLogEvent(code, message, consequence) -> *LogEvent{Code, Message}; consequence is appended after ” — ” at declaration.
• Log events share the errors’ VK serial space; the registry has one home, common/registry.go, and is generic: one map[string]Declaration behind the Declaration interface (GetCode/GetKind — Get-prefixed because Code is the field), one register func validating isVKCode + rejecting any registered code, one listRegistered[D] walker. Each kind’s file holds its type, constructor, Declaration methods, and its typed lister (Errors/LogEvents) — the registry knows no concrete kind.
• The declaration boundary mirrors [0553]: a Warn/Error event operator-actionable enough for a docs page declares; Debug/Info never.
• Declarations live in the owning vocabulary package’s logs.go (consumergroup, worker, cron) or beside the datastore’s errors.go when the event is package-local (producer create-ahead).
• Call sites log the declaration’s Message with "code", Event.Code as the first attr pair; the message stays static, the code is the pointer.
• 12 declarations, VK0026-VK0037; two dead-letter shapes stay two codes (per-batch commit vs per-delivery outcome — one code = one message).
• Docs pages stay on the one /errors/ path; vulkan explain lists and renders both kinds. tools/conventions walks cover event messages (banned words) and NewLogEvent codes (registry completeness).
• No Level field on LogEvent — the call site owns the level; pages state it by hand.

Consequences

• Operators grep a code, not wording; message text stays free to improve.
• Start-line snapshot rule finished: consumer start line carries message_timeout, shutdown_timeout, batch_limit; config-fact keys spell their config field snake_cased.