fix(ci): stop render:help failing when markdown-magic scans target/ (#14723)

<!-- entire-trail-link-start -->
https://entire.io/gh/jdx/mise/trails/908
<!-- entire-trail-link-end -->

The `lint` job in CI intermittently fails in `mise run render` with an
error like this:

```
Error: ENOENT: no such file or directory, lstat '.../target/debug/deps/serde_derive-....rcgu.o'
```

([failing
run](https://github.com/jdx/mise/actions/runs/39244920002/job/118037781515))

`render:help` ran `md-magic` (markdown-magic) with its default
`**/**.md` glob, which walks the whole tree including `target/`. When a
cargo step in the same job deleted an object file mid-walk, `lstat`
threw and the job failed.

No markdown file in the repo contains a markdown-magic block, so the
step does nothing. Running `md-magic` locally reports `Files with
transforms: 0` and changes no files. This PR removes the step from
`render:help`. It also removes the `wait_for = ["render:usage"]` that
existed only so markdown-magic would not scan `docs/cli` while it was
being replaced.

`render:help` now only runs `mise render-help`. The failing job can't be
re-run until its run finishes, so CI on this PR is the check.

*AI-assisted — Tool: Claude Code; model: anthropic/claude-sonnet-5-5;
version: unavailable.*

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Build-task-only change; drops a no-op doc step and does not alter
runtime or release behavior.
> 
> **Overview**
> Fixes intermittent CI failures in `mise run render` by simplifying the
**`render:help`** task.
> 
> **`render:help`** now only runs `mise render-help` (README /
`cli_commands.ts` generation). The **`markdown-magic`** (`md-magic`)
step is removed because it scanned `**/**.md` across the repo (including
`target/`) and could race with Cargo deleting build artifacts, and no
repo markdown uses markdown-magic blocks anyway.
> 
> The **`wait_for = ["render:usage"]`** guard is also removed; it
existed only to avoid `md-magic` walking `docs/cli` while `render:usage`
was replacing that directory.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
1b2d5b5931. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* The help-generation task now runs only the `mise` help-rendering step.
It no longer waits for the usage-rendering task or runs an additional
Markdown-processing step; the existing color setting and declared inputs
and outputs remain unchanged.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

tasks.toml

@@ -110,16 +110,10 @@ run = [
 ["render:help"]
 description = 'Render help documentation'
 depends = ["build"]
-# markdown-magic scans docs/cli while render:usage replaces that directory.
-# When both tasks are part of `mise run render`, wait for the replacement to finish.
-wait_for = ["render:usage"]
 env = { NO_COLOR = "1" }
 sources = ["mise"]
 outputs = ["README.md"]
-run = [
-  "mise render-help",
-  "mise run show-output-on-failure -- mise x node npm:markdown-magic -- md-magic",
-]
+run = "mise render-help"
 
 ["render:llms"]
 description = 'Generate docs/public/llms.txt (docs index for AI agents)'