Optimize restore-cached-apps job to eliminate unnecessary parallel runners

[Copilot]

• Resolves: dont rebuild already built apps #127 (comment)

Summary

The restore-cached-apps job spawned runners for ALL apps in the matrix, then each runner checked if it should skip. If 25/27 apps were cached, this meant 27 parallel runners where 25 immediately skipped—wasteful.

Changes

Matrix filtering in prepare-matrix job:

• Added apps-to-restore output containing only cached apps (inverse of apps-to-build)
• Built during cache detection step alongside apps-to-build list

Simplified restore-cached-apps job:

• Matrix now uses filtered apps-to-restore instead of full external-apps-matrix
• Removed Check if app needs restoring from cache step entirely
• Removed all if: steps.check-cache.outputs.skip == 'false' conditions
• Changed job condition from has-cached-apps == 'true' to apps-to-restore != '[]'

Result: If 25 apps are cached, exactly 25 runners spawn (not 27).

# Before: spawned 27 runners, 25 skipped immediately
matrix:
  app: ${{ fromJson(needs.prepare-matrix.outputs.external-apps-matrix) }}

# After: spawns only runners for cached apps
matrix:
  app_info: ${{ fromJson(needs.prepare-matrix.outputs.apps-to-restore) }}

TODO

N/A

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

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