ci+tests: oakstorage Windows URIs, Linux hang watchdog, cache-on-failure

oakstorage: the sqlite URI parse tests used /tmp/lib.db, which is not
absolute on Windows, so parse_target's is_absolute check rejected it.
Pick the absolute path per platform (C:/tmp/lib.db on Windows).

ci (Linux): wrap the test step in a 1500 s watchdog — a deadlocked
test prints nothing and never fails; on timeout the watchdog dumps
every test/worker process's thread stacks with gdb and then kills the
suite. (One such hang already ate a run; the previous green run needed
~4 min.)

ci+cd: Swatinem/rust-cache gains cache-on-failure everywhere, so a
red run still saves its compile cache (the actions/cache FFmpeg cache
already saves in its post phase regardless of outcome).

.github/workflows/cd.yml

@@ -101,6 +101,7 @@ jobs:
         uses: Swatinem/rust-cache@v2
         with:
           shared-key: oak-${{ matrix.distro }}
+          cache-on-failure: true
 
       - name: Cache project FFmpeg
         uses: actions/cache@v4
@@ -175,6 +176,7 @@ jobs:
         uses: Swatinem/rust-cache@v2
         with:
           shared-key: oak-appimage
+          cache-on-failure: true
 
       - name: Cache project FFmpeg
         uses: actions/cache@v4
@@ -241,6 +243,7 @@ jobs:
         uses: Swatinem/rust-cache@v2
         with:
           shared-key: oak-workspace
+          cache-on-failure: true
 
       - name: Cache project FFmpeg
         uses: actions/cache@v4
@@ -368,6 +371,7 @@ jobs:
         uses: Swatinem/rust-cache@v2
         with:
           shared-key: oak-workspace
+          cache-on-failure: true
 
       - name: Cache project FFmpeg
         uses: actions/cache@v4

.github/workflows/ci.yml

@@ -152,6 +152,7 @@ jobs:
         uses: Swatinem/rust-cache@v2
         with:
           shared-key: oak-workspace
+          cache-on-failure: true
 
       # The project FFmpeg (release/8.0, static, all free codecs + hwaccel)
       # is built by tooling/ffmpeg/build-ffmpeg.sh — 10-20 min on a cold
@@ -208,9 +209,30 @@ jobs:
 
       # xvfb + 24-bit screen: the gpui #[gpui::test] tests open real windows
       # and render through wgpu on Mesa's software Vulkan (lavapipe).
+      # The watchdog bounds the step: a deadlocked test produces no output
+      # and no failure, so after 1500 s (a green run needs ~4 min) it dumps
+      # every hung process's thread stacks and kills the suite.
       - name: Test (Linux)
         if: runner.os == 'Linux'
-        run: xvfb-run -a -s "-screen 0 1920x1080x24" cargo test --workspace --locked
+        run: |
+          sudo apt-get install -y gdb
+          xvfb-run -a -s "-screen 0 1920x1080x24" cargo test --workspace --locked &
+          TEST_PID=$!
+          (
+            sleep 1500
+            echo "::warning::test suite exceeded 1500s; dumping hung-process stacks"
+            for p in $(pgrep -f 'target/debug/deps/|target/debug/oak-worker'); do
+              echo "===== thread stacks of pid $p ($(readlink /proc/$p/exe 2>/dev/null)) ====="
+              sudo gdb -batch -ex 'thread apply all bt' -p "$p" || true
+            done
+            pkill -9 -f 'target/debug/deps/' || true
+            pkill -9 -f 'target/debug/oak-worker' || true
+          ) &
+          WATCHDOG_PID=$!
+          wait $TEST_PID
+          rc=$?
+          kill $WATCHDOG_PID 2>/dev/null || true
+          exit $rc
 
       # A crashing (SIGSEGV) test gives no Rust backtrace; rerun the
       # crashing test binaries under gdb to capture the native stack.

crates/oakstorage/src/backends/database/mod.rs

@@ -1484,13 +1484,21 @@ mod tests {
 		StorageUri::parse(s).unwrap()
 	}
 
+	/// An absolute database path for the platform: `/tmp/...` is not
+	/// absolute on Windows (no drive prefix), and parse_target rejects
+	/// relative paths.
+	#[cfg(unix)]
+	const ABS_DB: &str = "/tmp/lib.db";
+	#[cfg(windows)]
+	const ABS_DB: &str = "C:/tmp/lib.db";
+
 	#[test]
 	fn parse_target_sqlite_absolute() {
-		let t = parse_target(&uri("oakdb+sqlite:///tmp/lib.db")).unwrap();
+		let t = parse_target(&uri(&format!("oakdb+sqlite://{ABS_DB}"))).unwrap();
 		assert_eq!(
 			t,
 			DbTarget::Sqlite {
-				path: "/tmp/lib.db".to_string(),
+				path: ABS_DB.to_string(),
 				project: None
 			}
 		);
@@ -1498,11 +1506,14 @@ mod tests {
 
 	#[test]
 	fn parse_target_sqlite_project_query() {
-		let t = parse_target(&uri("oakdb+sqlite:///tmp/lib.db?project={abc-123}")).unwrap();
+		let t = parse_target(&uri(&format!(
+			"oakdb+sqlite://{ABS_DB}?project={{abc-123}}"
+		)))
+		.unwrap();
 		assert_eq!(
 			t,
 			DbTarget::Sqlite {
-				path: "/tmp/lib.db".to_string(),
+				path: ABS_DB.to_string(),
 				project: Some("{abc-123}".to_string())
 			}
 		);