Fix stale curated-resource pages surviving data refreshes

[LukasWallrich]

What Problem This Solves

Retired curated-resource rows could remain publicly accessible under /curated_resources/. The generator rewrote current rows without deleting files removed from the source sheet, and the deployment workflow overlaid generated artifacts on the checkout without clearing the generated directory.

Why This Change Was Made

• Remove generated resource files before regenerating the collection, while preserving _index.md.
• Clear the generated resource directory before the data artifact is unpacked during deployment.

This makes the generated collection a replacement of the source data rather than an additive merge.

User Impact

Pages for resources removed from the source sheet will no longer be rebuilt or remain in the deployed site. Current curated-resource URLs continue to be generated unchanged.

Evidence

• Focused generator replacement test passed: stale file removed and _index.md preserved.
• Focused deployment cleanup test passed.
• deploy.yaml parses as valid YAML.
• Python source compiles successfully.

Fixes #873

[github-actions]

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[github-actions]

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[LukasWallrich]

✅ Staging Deployment Status

This PR has been successfully deployed to staging as part of an aggregated deployment.

Deployed at: 2026-08-26 22:52:17 UTC
Staging URL: https://staging.forrt.org

The staging site shows the combined state of all compatible open PRs.