fix(ci): coverage floor failed on main — lower below the non-AVX-512 figure

.github/workflows/coverage.yml

@@ -38,14 +38,20 @@ jobs:
       - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # v2
       - name: Install cargo-llvm-cov (pinned)
         run: cargo install cargo-llvm-cov --version 0.8.7 --locked
-      # Generate the lcov report AND enforce the regression floor in a single
+      # Generate the lcov report AND enforce a regression floor in a single
       # --all-features invocation, so the floor is computed on exactly the data
-      # that gets uploaded — no separate `report` step that could differ in
-      # feature/package selection. On a regression this command exits non-zero
-      # (so the upload below is skipped). The floor sits well under the actual
-      # line coverage (~89%); raise it as coverage grows.
+      # that gets uploaded (no separate `report` step that could differ in
+      # selection). On a regression this command exits non-zero, so the upload
+      # below is skipped.
+      #
+      # The floor is 78%, set under the AVX-512-free figure: this runner has no
+      # AVX-512, so the runtime SIMD dispatch never reaches the AVX-512 kernels
+      # (bitmap / quant_kernels / sign_bitmap) and line coverage here is ~82%
+      # (vs ~90% on an AVX-512 host). Those kernels are exercised by the separate
+      # `avx512` job under Intel SDE. Follow-up: run THIS job under SDE too, for
+      # the full number and a tighter floor.
       - name: Generate coverage (lcov) + enforce floor
-        run: cargo llvm-cov --all-features --fail-under-lines 85 --lcov --output-path lcov.info
+        run: cargo llvm-cov --all-features --fail-under-lines 78 --lcov --output-path lcov.info
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@e79a6962e0d4c0c17b229090214935d2e33f8354 # v6.0.1
         with: