[guidelines] side-quest-07d-billing-paths.md: missing page annotation schema

## File reviewed
`workshop/side-quest-07d-billing-paths.md`

## Violations

### Missing workshop page annotation schema
**Offending text:**
> (file starts directly with `# Side Quest: Copilot Billing Paths` — no annotation comments precede it)

**Suggested fix:**
Add the required two-line annotation block as the very first content in the file, before the `#` heading, per the "Workshop page annotation schema" rule in `.github/workflows/guidelines.md`:
```

```
`journey: all` fits because the page applies regardless of environment (Codespace, local, or UI-only paths are all referenced), and `adventure: side-quest` matches the filename pattern `side-quest-NN-MM-.md`. Confirm these values against the neighboring `06-03*` and `08-01` side quest files before committing.

> Generated by [📋 Guidelines Enforcer](https://github.com/githubnext/gh-aw-workshop/actions/runs/34736492618) · copilot · auto · 97 AIC · ⌖ 6.78 AIC · ⊞ 9.5K · [◷](https://github.com/search?q=repo%3Agithubnext%2Fgh-aw-workshop+is%3Aissue+%22gh-aw-workflow-call-id%3A+githubnext%2Fgh-aw-workshop%2Fguidelines-enforcer%22&type=issues)
> - [x] expires on Sep 20, 2026, 3:59 AM UTC

Open workshop/side-quest-07d-billing-paths.md and read the Workshop page annotation schema rule in .github/workflows/guidelines.md. Compare the annotation values with neighboring 06-03* and 08-01 side quest files. Done means the required two comment lines are the first content before the heading and match the documented schema.

Written by the indexing model from the issue text.