v2.4.2: post-merge fixes copied from old zsa1-v2.4.2-fixes

This commit applies the cumulative post-merge fixes on top of
`zsa1-v2.4.2-conflicts-new` by copying the file states from the tip of
`zsa1-v2.4.2-fixes` (old stack), without re-resolving conflicts.

Context:
- Base: zsa1-v2.4.2-conflicts-new (upstream v2.4.2 import)
- Source of fixes: zsa1-v2.4.2-fixes@<OLD_SHA>

Contents (intent):
- Conflict resolutions carried over from the old stack
- Build and test follow-ups required after v2.4.2 import
- No intentional behavior changes beyond integration fixes

Notes:
- This is a squash-style carryover to keep the new PR stack reviewable.
- For provenance, see the original fixes branch at <OLD_SHA>.

Refs: upstream v2.4.2, zsa1

Author: dmidem

.github/workflows/ci-basic.yml

@@ -25,7 +25,16 @@ jobs:
       - name: Install formatting & linting tools
         run: rustup component add rustfmt clippy
       - name: Run tests
-        run: cargo test --verbose
+        env:
+          RUST_BACKTRACE: 1
+        # Skip two tests that intermittently fail on CI (likely a race/ordering issue).
+        # FIXME: investigate and fix the underlying flake; remove these skips once resolved.
+        run: cargo test --locked --verbose -- --skip v4_with_sapling_spends --skip v5_with_sapling_spends
+      # Run the skipped tests separately with constrained parallelism
+      - name: Run Sapling spend tests
+        run: |
+          cargo test -p zebra-consensus v4_with_sapling_spends -- --nocapture
+          cargo test -p zebra-consensus v5_with_sapling_spends -- --nocapture
       - name: Verify working directory is clean
         run: git diff --exit-code
       - name: Run doc check