review: one text per usage and content query, rendered per dialect

[CMGS]

What

crates/state/src/store.rs: the six Store methods that were written once for SQLite and once for Postgres (ledger_usage, usage_by_user, usage_series, security_events, content_list_user, and the INSERT of usage_rollup_advance) now share one query text each. The two copies differed only in four dialect tokens — ::BIGINT on SUM, ::text on a nullable parameter, GREATEST vs MAX, ''::text — so each query is a macro_rules! taking the dialect (sql_bigint!, sql_text!, sql_greatest!, sql_opt_eq!, usage_sums!), and the methods live in the shared sql_store_impl! body. usage_rollup_advance keeps its two bodies because Postgres takes an advisory lock; only its INSERT text is shared. content_erase_user, file_put and the batch methods stay dialect-bound (they differ in statements, not tokens).

Net −81 production lines (+322/−403), +88 test lines.

The placeholder trap, handled

The shared text uses numbered ?N placeholders because two of the queries repeat ?1/?2 and bind ?5 before ?4. pg_numbered used to renumber every ? by position, which would have turned ?1 into $11; it now keeps a numbered ?N as $N and only counts up bare ?. Its unit test covers MAX(?3, ?5) AND ?4 OR ?1.

Evidence that the SQL each backend runs is unchanged

• shared_sql_renders_the_pre_share_text_per_dialect: renders all ten shared texts for both dialects and compares them, whitespace-normalised, with the literal text each backend carried before this change (the expected strings in the test are the pre-share literals).
• cargo fmt --all -- --check, cargo clippy --workspace --all-targets -- -D warnings, cargo test --workspace: clean on macOS and in the pinned rust:1.98.0 linux/arm64 container (gw-state: 84 passed).
• Postgres suite executed, not skipped: GW_TEST_PG_URL against a fresh postgres:16-alpine container — postgres_store_roundtrip, pg_rollup_and_erase_roundtrip, postgres_finalize_sees_result_committed_during_lock_wait, postgres_keystore_semantics_mirror_memory, publish_notifies_and_load_returns_latest all pass (84 passed, 0 failed); the run created database gwtest_1788530106228119000 on the server.
• Comment lines: +3 −4.