0628 — The table-name functions are public API

Context. [0371] moved MessageLogTable and its siblings into internal/topic on the premise that they were cross-package plumbing: “zero example programs call them, and every real call site is pkg/producer/pkg/consumer building raw SQL against tables pkg/topic owns.” That premise no longer holds. Labs cannot import internal/, so every lab that touches a per-topic table interpolates message_log_%d by hand, and CONVENTIONS ## Tables had to carry a standing exception saying so — a second way of spelling a name the library already computes one way, which is exactly the duplicate-mechanism smell the file bans. The schema work [0629] adds a second caller the internal package cannot serve: an operator pasting a diagnose query needs the table’s real name, and per-topic names are the half no catalog lookup gives them.

Decision. internal/topic/tables.go becomes pkg/topic/tables.go; the twelve funcs are public API on the vocabulary root. Every call site drops the iTopic alias and spells the package topic — the alias existed only because [0371]‘s pkg/topic/datastore.go held local topic *Topic variables that would shadow it, and that file is gone. The repo-root internal/ directory held nothing else and is deleted. CONVENTIONS ## Tables loses the lab exception: everything names a per-topic table through these funcs.

Consequences. Supersedes [0371], which is marked superseded. Twelve function names join the public surface permanently and cannot be renamed without a breaking change — accepted, because a per-topic table’s name is already public in every sense that matters: it is in the DDL, in error text, and in the diagnose queries. tools/conventions’s DDL walk reads the funcs from their new path. Rejected: keeping the funcs internal and giving labs a duplicate helper — two derivations of one name is the thing [0371]‘s exception already was.