docs: the What's New popup carries release numbers, never dates

AGENTS.md

@@ -381,3 +381,21 @@ The company is always the **customer's** company (`customer.company`), never
   `--apply` `scripts/2026-10-31-backfill-company-letterheads.ts` (fills companies
   whose rendered quotes all used one letterhead). Until the migration runs the
   lock is off and everything behaves as before.
+
+# What's New (sidebar popup) — release numbers and commits, never dates
+
+The sidebar's "What's New" popup lists releases from `src/lib/release-notes.ts` — a
+hand-written array, newest first. There is no changelog table and no fetch: the notes are
+typed in when a release goes out. The "New" badge lights up when the top entry's release
+number differs from `wfdash-whats-new-seen` in the operator's localStorage.
+
+- A release is identified by **its number** and **the short SHA of the commit it went out
+  with** (`commit`). The SHA is plain text — never a link; the Forgejo instance is on an
+  internal host.
+- **No dates on screen.** The `date` field in the data file is an authoring reference only
+  (which window of commits a release covers) and is never rendered. The date formatter was
+  deleted, so there is no code path that can turn a date into text, and
+  `src/components/whats-new-dialog.test.tsx` fails the build if a date comes back.
+- To publish a release: merge, take `git log --oneline -1`, add an entry at the top with the
+  next number (the next one after this change is 6) and that SHA. The number is the "seen"
+  marker — bumping it re-notifies everyone.