📝 Track the undocumented use: prefix in the backlog

`use:git-commit-message` is referenced by CONTRIBUTING.md but appears in
none of the lists that define the script vocabulary, so the rule "reuse
an existing prefix, never invent one" is currently violated by its own
exception.

Recorded as a task rather than fixed here: the prefix wants a name that
says what it is for, and that is the same decision as naming a prefix
for the other lifecycle scripts, so the two should be chosen together.

backlog.tasks

@@ -18,6 +18,10 @@ Setup:
     - maybe skills?
     → resolved: adopted @spences10/pi-lsp@0.0.46 as a project-local pi extension (`.pi/settings.json`). It auto-detects the repo's TypeScript 7 (no `lib/tsserver.js`) and spawns `tsc --lsp --stdio` — the same tsgo binary VS Code's native-preview uses. Read-only: hover / definition / references / symbols / diagnostics. No skill; skills don't own persistent processes.
 
+☐ Adopt a `setup:` prefix for one-time clone configuration
+    ☐ Register `use:git-commit-message` as its first member (and retire `use:` — it is in no prefix list)
+    ☐ Create an umbrella 'setup' task that runs all setup tasks - currently one
+
 v1.0:
 ☐ API surface is stable and fully typed
     ☐ Finalize public exports in `src/index.ts`