Fix/panicbot colon filename (#456)

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SPDX-License-Identifier: CC-BY-SA-4.0
Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
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## Summary

<!-- What does this PR do, and why? -->

Closes #

## Type of change

- [ ] 🐛 Bug fix (non-breaking change that fixes an issue)
- [ ] ✨ New feature (non-breaking change that adds functionality)
- [ ] 💥 Breaking change (would change existing behaviour)
- [ ] 🕳️ Soundness fix (fixes a checker/proof false-negative)
- [ ] 📖 Documentation
- [ ] 🧹 Refactor / tech debt (behaviour-preserving)
- [ ] ⚡ Performance
- [ ] 🔧 Build / CI / tooling

## How has this been verified?

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## Checklist

- [ ] My commits are **signed** (`git commit -S`).
- [ ] I ran the project's own checks/tests locally and they pass.
- [ ] New files carry the correct `SPDX-License-Identifier` (code/config
`MPL-2.0`,
      prose `CC-BY-SA-4.0`); I did not relicense existing files.
- [ ] Docs are updated, and no public claim now overstates what the code
does.
- [ ] I have not introduced a soundness hole (or I have flagged where I
might have).

## Notes for reviewers

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----
## Summary by Gitar

- **CI improvements:**
- Added guard in `panicbot-sweep.yml` to fail on artifact-illegal
colon-named finding files
- Updated permissions for the secret scanner job in `secret-scanner.yml`

<sub>This will update automatically on new commits.</sub>

---------

Signed-off-by: Jonathan D.A. Jewell <6759885+hyperpolymath@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/secret-scanner.yml

@@ -20,4 +20,4 @@ jobs:
       pull-requests: write
       actions: read
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@e9c8888769a703924cc3c0d717900960d78aea00
-    secrets: inherit
+    secrets: inherit