workflows/check: don't check github api for owners file

This removes the "owners" check from codeowners-validator. With it, all
tokens and permissions can be removed, because these were only needed to
make these requests.

This solves the problem of codeowners-validator not supporting our new
nested team structure for nixpkgs-maintainers. To make the onboarding of
new teams easier, we moved all teams "under" the nixpkgs-maintainers
team. This makes them inherit the right privileges (triage) for Nixpkgs.

However, this inheritance is not recognized by codeowners-validator,
thus it assumes that these teams don't have access to Nixpkgs. This then
fails the owners check immediately.

Removing the owners check also has a few other advantages:
- This check depends on external state: If a user is renamed or a team
removed, the check will fail. This makes it a bad check for required
status checks or merge queues - the check might fail randomly,
independent of the current PR.
- Running this check in a fork will never work, because the respective
users and teams don't have access to the fork's repo.

Both of this required us to set `continue-on-error: true` most of the
time.

.github/workflows/check.yml

···
       mergedSha:
         required: true
         type: string
-      ownersCanFail:
-        required: true
-        type: boolean
       targetSha:
         required: true
         type: string
     secrets:
       CACHIX_AUTH_TOKEN:
-        required: true
-      OWNER_RO_APP_PRIVATE_KEY:
         required: true
 
 permissions: {}
···
           GH_TOKEN: ${{ github.token }}
         run: gh api /rate_limit | jq
 
-  # For checking code owners, this job depends on a GitHub App with the following permissions:
-  # - Permissions:
-  #   - Repository > Administration: read-only
-  #   - Organization > Members: read-only
-  # - Install App on this repository, setting these variables:
-  #   - OWNER_RO_APP_ID (variable)
-  #   - OWNER_RO_APP_PRIVATE_KEY (secret)
-  #
-  # This should not use the same app as the job to request reviewers, because this job requires
-  # handling untrusted PR input.
   owners:
     runs-on: ubuntu-24.04-arm
-    continue-on-error: ${{ inputs.ownersCanFail }}
     timeout-minutes: 5
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
···
         uses: ./.github/actions/checkout
         with:
           merged-as-untrusted-at: ${{ inputs.mergedSha }}
-          target-as-trusted-at: ${{ inputs.targetSha }}
 
       - uses: cachix/install-nix-action@a809471b5c7c913aa67bec8f459a11a0decc3fce # v31
 
···
           pushFilter: -source$
 
       - name: Build codeowners validator
-        run: nix-build nixpkgs/trusted/ci --arg nixpkgs ./nixpkgs/trusted-pinned -A codeownersValidator
-
-      - uses: actions/create-github-app-token@67018539274d69449ef7c02e8e71183d1719ab42 # v2.1.4
-        if: github.event_name == 'pull_request_target' && vars.OWNER_RO_APP_ID
-        id: app-token
-        with:
-          app-id: ${{ vars.OWNER_RO_APP_ID }}
-          private-key: ${{ secrets.OWNER_RO_APP_PRIVATE_KEY }}
-          permission-administration: read
-          permission-members: read
-
-      - name: Log current API rate limits
-        if: steps.app-token.outputs.token
-        env:
-          GH_TOKEN: ${{ steps.app-token.outputs.token }}
-        run: gh api /rate_limit | jq
+        run: nix-build nixpkgs/untrusted/ci --arg nixpkgs ./nixpkgs/untrusted-pinned -A codeownersValidator
 
       - name: Validate codeowners
-        if: steps.app-token.outputs.token
         env:
           OWNERS_FILE: nixpkgs/untrusted/ci/OWNERS
-          GITHUB_ACCESS_TOKEN: ${{ steps.app-token.outputs.token }}
           REPOSITORY_PATH: nixpkgs/untrusted
-          OWNER_CHECKER_REPOSITORY: ${{ github.repository }}
+          # Omits "owners", which checks whether GitHub handles exist, but fails with nested team
+          # structures.
+          CHECKS: "duppatterns,files,syntax"
           # Set this to "notowned,avoid-shadowing" to check that all files are owned by somebody
           EXPERIMENTAL_CHECKS: "avoid-shadowing"
         run: result/bin/codeowners-validator
-
-      - name: Log current API rate limits
-        if: steps.app-token.outputs.token
-        env:
-          GH_TOKEN: ${{ steps.app-token.outputs.token }}
-        run: gh api /rate_limit | jq

.github/workflows/pr.yml

···
       OWNER_APP_PRIVATE_KEY:
         # The Test workflow should not actually request reviews from owners.
         required: false
-      OWNER_RO_APP_PRIVATE_KEY:
-        required: true
 
 concurrency:
   group: pr-${{ github.workflow }}-${{ github.event_name }}-${{ github.event.pull_request.number || github.run_id }}
···
       pull-requests: write
     secrets:
       CACHIX_AUTH_TOKEN: ${{ secrets.CACHIX_AUTH_TOKEN }}
-      OWNER_RO_APP_PRIVATE_KEY: ${{ secrets.OWNER_RO_APP_PRIVATE_KEY }}
     with:
       baseBranch: ${{ needs.prepare.outputs.baseBranch }}
       headBranch: ${{ needs.prepare.outputs.headBranch }}
       mergedSha: ${{ needs.prepare.outputs.mergedSha }}
       targetSha: ${{ needs.prepare.outputs.targetSha }}
-      ownersCanFail: ${{ !contains(fromJSON(needs.prepare.outputs.touched), 'owners') }}
 
   lint:
     name: Lint

.github/workflows/test.yml

···
     secrets:
       CACHIX_AUTH_TOKEN: ${{ secrets.CACHIX_AUTH_TOKEN }}
       NIXPKGS_CI_APP_PRIVATE_KEY: ${{ secrets.NIXPKGS_CI_APP_PRIVATE_KEY }}
-      OWNER_RO_APP_PRIVATE_KEY: ${{ secrets.OWNER_RO_APP_PRIVATE_KEY }}
 
   push:
     if: needs.prepare.outputs.push

ci/github-script/prepare.js

···
 
     const touched = []
     if (files.includes('ci/pinned.json')) touched.push('pinned')
-    if (files.includes('ci/OWNERS')) touched.push('owners')
     core.setOutput('touched', touched)
 
     return