ci(prd): require manual numbering before merge

AGENTS.md

@@ -44,10 +44,10 @@ backend remains available with `BOT_BOTTLE_BACKEND=docker` or
 
 - Three kinds of doc, each with its own conventions in-folder; see
   `docs/README.md` for when to write which:
-  - **PRDs** (`docs/prds/`) — one feature per file. While a PR is open
-    the file is named `prd-new-<kebab>.md`; CI assigns a sequential
-    number on merge to `main` and renames it. A `Status:` line tracks
-    lifecycle: Draft → Active (shipped to `main`) →
+  - **PRDs** (`docs/prds/`) — one feature per file. A draft may initially
+    use `prd-new-<kebab>.md`, but its author must assign the next
+    sequential number before merge; CI rejects unnumbered PRDs. A
+    `Status:` line tracks lifecycle: Draft → Active (shipped to `main`) →
     Superseded/Retargeted. Format in `docs/prds/README.md`.
   - **Research notes** (`docs/research/`) — opinionated investigations;
     unnumbered kebab-case, freeform and verdict-first. See