refactor(ci): drop upload/download-artifact (remove github.com dependency)

actions/upload-artifact and download-artifact run code fetched from
github.com (and v4 is GHES-incompatible, v3 deprecated). The runner
host is single with a shared filesystem, so the orchestrator's
host-side collect dir is the artifact handoff:

- action.yml: replace the two upload-artifact steps with
  host-path report steps; artifacts stay under F:\CI\Artifacts and
  are aged by Invoke-RetentionPolicy.ps1.
- build-nsInnoUnp.yml: release job reads
  F:\CI\Artifacts\{run_id}-{run_attempt}-{target} directly instead of
  download-artifact; existing Gitea REST release-asset upload unchanged.

Tradeoff (accepted): artifacts are no longer downloadable from the
Gitea Actions run page for non-tag builds — only on host disk, and as
release assets for tagged builds.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/build-nsInnoUnp.yml

@@ -46,18 +46,10 @@ jobs:
     runs-on: windows-build
 
     steps:
-      - name: Download Windows artifact
-        uses: actions/download-artifact@v3
-        with:
-          name: nsis-plugin-nsinnounp-windows-${{ github.ref_name }}
-          path: artifacts/windows
-
-      - name: Download Linux artifact
-        uses: actions/download-artifact@v3
-        with:
-          name: nsis-plugin-nsinnounp-linux-${{ github.ref_name }}
-          path: artifacts/linux
-
+      # No actions/download-artifact (its code is fetched from github.com).
+      # The runner host is single and shared; the build matrix legs left
+      # their outputs at F:\CI\Artifacts\{run_id}-{run_attempt}-{target}
+      # (job-id-suffix = matrix.target). Read them directly from disk.
       - name: Create Gitea release and upload assets
         shell: powershell
         env:
@@ -65,6 +57,8 @@ jobs:
           GITEA_URL:   ${{ github.server_url }}
           REPO:        ${{ github.repository }}
           TAG:         ${{ github.ref_name }}
+          RUN_ID:      ${{ github.run_id }}
+          RUN_ATTEMPT: ${{ github.run_attempt }}
         run: |
           #Requires -Version 5.1
           Set-StrictMode -Version Latest
@@ -86,9 +80,15 @@ jobs:
           $releaseId = $release.id
           Write-Host "Release created: id=$releaseId name=$($release.name)"
 
-          # Compress each artifact directory and upload as a release asset
+          # Compress each host-side artifact directory and upload as a
+          # release asset. The build legs collected to
+          # F:\CI\Artifacts\{run_id}-{run_attempt}-{target}.
           foreach ($target in @('windows', 'linux')) {
-              $srcDir  = "artifacts\$target"
+              $srcDir  = "F:\CI\Artifacts\$env:RUN_ID-$env:RUN_ATTEMPT-$target"
+              if (-not (Test-Path -LiteralPath $srcDir) -or
+                  -not (Get-ChildItem -Force -LiteralPath $srcDir)) {
+                  throw "artifact dir missing or empty: $srcDir"
+              }
               $zipName = "nsis-plugin-nsinnounp-$target-$env:TAG.zip"
               Compress-Archive -Path "$srcDir\*" -DestinationPath $zipName -Force