docs: tag the untagged verifications, and record the UR-007 conflict

Five tests and the schema constant implemented requirements without
carrying a tag, so those requirements read as uncovered when they were
not. No behaviour changes here — every edit is a comment.

Also documents `static` as a real tier rather than an exemption: it is
already in `ci_executable_tiers` and its checks run in CI, and it exists
because DR-007's single binary and DR-012's licence policy are properties
of the build that a unit test could only assert as theatre.

The UR-007 note records a cross-repo status conflict rather than
resolving it. `jRay` JR-025 is `Done` and claims UR-007, but the fetch
path that would exercise it (`jRay` JR-031) is still `Planned`. Either
JR-025 is scoped to selection alone or it over-claims; until that is
settled neither register should be trusted for UR-007 coverage.

The gate reports 0 orphan tags and 19/19 UR coverage.

TRACES: DR-001, DR-014, UR-015, UR-016, UR-018 | SR-003, SR-004

src/db/mod.rs

@@ -22,6 +22,12 @@ use std::sync::{Arc, Mutex};
 use anyhow::Context;
 use rusqlite::Connection;
 
+/// The whole schema, as portable SQL — it runs unchanged on Postgres, so
+/// SQLite-specific forms (`INSERT OR REPLACE`) are avoided in favour of the
+/// standard `INSERT ... ON CONFLICT` (§8). Keeping it in one `.sql` file rather
+/// than scattered through the repository is what makes that reviewable.
+///
+/// TRACES: DR-014 | PR-004
 const SCHEMA: &str = include_str!("schema.sql");
 
 /// Handle to the database: one serialized writer, plus read connections.