Add clang-format, clang-tidy, ASan/UBSan CI lanes

Format and tidy enforce only on lines changed in PRs (diff-only via
git-clang-format and clang-tidy-diff.py) — existing files keep their
current style until edited. Mass reformat deferred; .git-blame-ignore-revs
stub is in place for whenever that happens.

Sanitizer lane builds with -fsanitize=address,undefined and runs the
unit suite. continue-on-error: true initially so we can triage findings
without blocking PRs. UB categories pervasive in the Hash9 C cascade
(alignment, signed-integer-overflow, vptr) are suppressed pending
file-by-file fixes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/build-all.yml

@@ -37,6 +37,50 @@ jobs:
       - name: Run unit tests
         run: cd build && ctest --output-on-failure || true
 
+  test-linux-sanitizers:
+    # ASan + UBSan build of the daemon + unit tests. Allowed to fail until
+    # findings are triaged — see .github/workflows/lint.yml comment block.
+    # Once the test suite is clean under sanitizers, drop continue-on-error.
+    runs-on: ubuntu-22.04
+    continue-on-error: true
+    env:
+      # ASan: leak detection off by default (BDB and OpenSSL produce noise on shutdown).
+      # Re-enable once we've quieted the legitimate suspects.
+      ASAN_OPTIONS: "detect_leaks=0:halt_on_error=1:abort_on_error=1:print_stacktrace=1:strict_string_checks=1:detect_stack_use_after_return=1"
+      # UBSan: print full stack traces on first error and exit non-zero.
+      UBSAN_OPTIONS: "halt_on_error=1:abort_on_error=1:print_stacktrace=1"
+      # Suppress UB categories that are pervasive in the Hash9 C cascade
+      # and BDB until they're fixed file-by-file.
+      SAN_FLAGS: "-fsanitize=address,undefined -fno-omit-frame-pointer -fno-sanitize-recover=undefined -fno-sanitize=alignment,signed-integer-overflow,vptr"
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential cmake ninja-build \
+            libboost-all-dev libssl-dev libdb++-dev libleveldb-dev \
+            libevent-dev libminiupnpc-dev zlib1g-dev
+
+      - name: Configure with sanitizers
+        run: |
+          cmake -B build-san -G Ninja \
+            -DCMAKE_BUILD_TYPE=Debug \
+            -DCMAKE_C_FLAGS="$SAN_FLAGS" \
+            -DCMAKE_CXX_FLAGS="$SAN_FLAGS" \
+            -DCMAKE_EXE_LINKER_FLAGS="$SAN_FLAGS" \
+            -DCMAKE_SHARED_LINKER_FLAGS="$SAN_FLAGS" \
+            -DBUILD_QT=OFF \
+            -DBUILD_DAEMON=ON \
+            -DBUILD_TESTS=ON \
+            -DUSE_UPNP=OFF
+
+      - name: Build
+        run: cmake --build build-san -j$(nproc)
+
+      - name: Run unit tests under sanitizers
+        run: cd build-san && ctest --output-on-failure
+
   build-windows-qt:
     runs-on: windows-latest
     defaults: