♻️ Group workflow scripts under a create: prefix

`branch` and `release` were bare commands, but bare in this repo means
"how you invoke a tier" or "runs one tool" — neither fits a command that
opens or closes a unit of work. They get their own prefix now, since a
prefix is how this repo records _when_ a script runs.

`create:` because both members genuinely create something (a branch, a
release) and it is a plain verb rather than VCS slang. No bare `create`
aggregator: running "all the workflows" describes nothing anyone wants,
and `publish:*` already precedents a prefix without one.

The rule "reuse an existing prefix, never invent one" now says what it
actually means: a new prefix is allowed when the scripts belong in the
pipeline, provided it enters both lists in the same commit as its first
member. That is the lesson from `use:`, which is referenced by prose yet
in none of the lists — already tracked in backlog.tasks.

The bare-command sentence shrinks to `build`, `clean`, `verify`.

AGENTS.md

@@ -41,7 +41,7 @@ Never start a long-lived / blocking process such as `npm run watch`. It runs unt
 
 ### Working on tasks
 
-- **Task with subtasks** (a task that has indented children): create the branch with `npm run branch -- <prefix>/<desc>`, inferring the prefix from the task content (`feature/…` / `fix/…` / `chore/…`) — do not hand-write `git switch -c`, the command enforces the clean-tree / current-`main` / green-baseline precondition. Work on each subtask with commits, then present a concise handover for the user to review. Use this fixed shape:
+- **Task with subtasks** (a task that has indented children): create the branch with `npm run create:branch -- <prefix>/<desc>`, inferring the prefix from the task content (`feature/…` / `fix/…` / `chore/…`) — do not hand-write `git switch -c`, the command enforces the clean-tree / current-`main` / green-baseline precondition. Work on each subtask with commits, then present a concise handover for the user to review. Use this fixed shape:
 
     ```md
     ## Handover — <branch>