feat(#1997): add prettier markdown formatter to treefmt

- .prettierrc: proseWrap=preserve (no prose reflow)
- .prettierignore: exclude hivectl-cli.md (auto-generated) + 11 docs
  with multi-line list-item continuations prettier would strip to col 0
  (CommonMark limitation in prettier's list handling)
- format 16 markdown files: cosmetic only (*→_, table alignment,
  heading normalisation) — verified no broken continuations, idempotent

docs/tools/bash.md

@@ -15,17 +15,18 @@ Submit a shell command for background execution (runs via `bash`).
 Stdout and stderr stream to `harness/bash-tasks/<id>.{out,err}`.
 When the task completes (or times out, or the process errors), the
 harness fires a wake with `from: "bash-task-<id>"` and the exit code
-+ last stdout lines in the body; handle it on a future turn.
 
-- `timeout_secs` — kill the task after N seconds and mark it
+- last stdout lines in the body; handle it on a future turn.
+
+* `timeout_secs` — kill the task after N seconds and mark it
   `timed_out`. Omit for no timeout (runs until natural exit).
-- `wait_seconds` — inline poll before returning (capped at 30).
+* `wait_seconds` — inline poll before returning (capped at 30).
   When the task finishes within the window the full status is
   returned immediately and no wake is fired; when the window expires
   the task keeps running and the normal `task started: id=<id>`
   response is returned. **Defaults to 3** — pass `wait_seconds: 0`
   to disable inline waiting and always get the immediate response.
-- `name` — optional caller-chosen task id. When set it replaces the
+* `name` — optional caller-chosen task id. When set it replaces the
   auto-generated hex id, so it surfaces in the wake `from`
   (`bash-task-<name>`), in `status(<name>)` lookups, and in the
   loose-ends list — a memorable label instead of an opaque id. A name