Add Linux unit test CI job, TRY_LOCK for GUI, gitignore cleanup

- Add test-linux-unit CI job; release now depends on tests passing
- Replace LOCK(cs_wallet) with TRY_LOCK in transactiontablemodel to avoid GUI freezes
- Add build artifacts to .gitignore (dist/, zips, object scripts)
- Add unit test instructions to README

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/build-all.yml

@@ -12,6 +12,29 @@ env:
   VERSION: "5.3.6"
 
 jobs:
+  test-linux-unit:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential libboost-all-dev \
+            libssl-dev libdb++-dev libleveldb-dev libevent-dev libminiupnpc-dev
+
+      - name: Build LevelDB
+        run: |
+          cd src/leveldb
+          chmod +x build_detect_platform
+          make clean || true
+          make OPT="-O2" libleveldb.a libmemenv.a
+
+      - name: Run unit tests
+        run: |
+          cd src
+          make -f makefile.unix test -j$(nproc)
+
   build-windows-qt:
     runs-on: windows-latest
     defaults:
@@ -259,7 +282,7 @@ jobs:
 
   release:
     if: startsWith(github.ref, 'refs/tags/v')
-    needs: [build-windows-qt, build-windows-daemon, build-linux-qt, build-linux-daemon, build-macos]
+    needs: [test-linux-unit, build-windows-qt, build-windows-daemon, build-linux-qt, build-linux-daemon, build-macos]
     runs-on: ubuntu-latest
     permissions:
       contents: write