fix(amazonq): @-prompts not added to context

[avi-alpert]

Problem

@Prompts not being sent to context due to change in last week's release

Solution

Add 'file' label to user prompts

---

• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.