ci: drop per-PR Windows release build; bind to release tags (#155)

The `test_windows_binaries` job ran a full Windows --release build +
smoke test on every code PR. It was a non-required (non-blocking) check,
so it never gated a merge — it only burned the slowest/most expensive
runner (windows-latest, --release, 75-min ceiling) on every code change.

Windows binary validation is already covered (better) on release tags:
release.yml's `smoke_windows_installer` (on v* tags) builds the release
binaries, installs via scripts/install.ps1, and smoke-runs
`omnigraph.exe version` + `omnigraph-server.exe --help` — the same smoke
test plus the real installer path. Nothing `needs:` the removed job.

Trade-off (accepted): a PR that breaks the Windows build or install.ps1
syntax is now caught at release-cut rather than at PR time. install.ps1
and platform-specific code change rarely; the cost savings on every PR
outweigh the earlier signal.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -261,63 +261,6 @@ jobs:
         if: needs.classify_changes.outputs.run_full_ci == 'true'
         run: cargo test --locked -p omnigraph-server --features aws
 
-  test_windows_binaries:
-    name: Test Windows release binaries
-    needs: classify_changes
-    runs-on: windows-latest
-    timeout-minutes: 75
-    permissions:
-      contents: read
-    env:
-      CARGO_TERM_COLOR: always
-    steps:
-      - name: Skip for text-only changes
-        if: needs.classify_changes.outputs.run_full_ci != 'true'
-        run: Write-Host "Text-only change detected; skipping Windows binary build."
-
-      - name: Checkout source
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        uses: actions/checkout@v5.0.1
-
-      - name: Install system dependencies
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        run: choco install protoc -y
-
-      - name: Install Rust stable
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        uses: dtolnay/rust-toolchain@stable
-        with:
-          toolchain: stable
-
-      - name: Cache Rust build data
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        uses: Swatinem/rust-cache@v2
-        with:
-          workspaces: |
-            . -> target
-          key: windows-release-binaries
-
-      - name: Build Windows binaries
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        run: cargo build --release --locked -p omnigraph-cli -p omnigraph-server
-
-      - name: Smoke test Windows binaries
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        run: |
-          & ./target/release/omnigraph.exe version
-          & ./target/release/omnigraph-server.exe --help
-
-      - name: Check PowerShell installer syntax
-        if: needs.classify_changes.outputs.run_full_ci == 'true'
-        run: |
-          $tokens = $null
-          $errors = $null
-          [System.Management.Automation.Language.Parser]::ParseFile("scripts/install.ps1", [ref]$tokens, [ref]$errors) | Out-Null
-          if ($errors.Count -gt 0) {
-            $errors | Format-List
-            exit 1
-          }
-
   rustfs_integration:
     name: RustFS S3 Integration
     needs: