ci: self-hosted runner workflow for qbz-slint (real artifact path)

The GitHub-hosted private runner is 2 vCPU/8 GB and cannot build qbz-slint
(died at 1h42m). The dev box CAN, so a self-hosted runner (qbz-box) gives a
reliable CI artifact. Manual trigger; uncapped threads=2 (box-proven);
persistent work dir = incremental after first build.

cc

.github/workflows/build-slint-selfhosted.yml

@@ -0,0 +1,54 @@
+name: Build Slint (self-hosted)
+
+# Builds qbz-slint on the self-hosted runner registered on the dev box
+# (`qbz-box`, labels: self-hosted,linux,x64,qbz-builder). The box CAN compile
+# qbz-slint (proven locally), so this is the reliable path to a real CI/CD
+# artifact while the GitHub-hosted private runner (2 vCPU / 8 GB) cannot.
+#
+# Self-hosted runners keep their work directory between runs, so `target/`
+# persists → builds are INCREMENTAL after the first (no `actions/cache` needed).
+#
+# MANUAL trigger only (workflow_dispatch): the box shares RAM with the desktop
+# and earlyoom will SIGTERM the build if RAM runs low. Trigger this when the box
+# is free (close heavy apps / TTY), and do NOT run a local build at the same
+# time (one heavy build at a time — the box hard-freezes on double-build OOM).
+
+on:
+  workflow_dispatch:
+
+concurrency:
+  group: selfhosted-slint
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: [self-hosted, qbz-builder]
+    timeout-minutes: 180
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Free RAM check (earlyoom will kill the build if too low)
+        run: |
+          free -h | head -2
+          avail=$(free -m | awk '/^Mem:/ {print $7}')
+          echo "MemAvailable: ${avail} MB"
+          if [ "${avail}" -lt 16000 ]; then
+            echo "::warning::Only ${avail} MB free — earlyoom may SIGTERM the qbz-slint rustc. Close apps / drop to TTY for headroom."
+          fi
+
+      - name: Build qbz-slint (box-proven settings — uncapped, threads=2)
+        run: NORUN=1 CAPPED=0 THREADS=2 ./scripts/slint-run.sh
+
+      - name: Strip + report size
+        run: |
+          BIN=crates/target/release/qbz-slint
+          echo "unstripped:"; ls -lh "$BIN" | awk '{print $5}'
+          cp "$BIN" qbz-slint-linux-x86_64
+          strip qbz-slint-linux-x86_64 || true
+          echo "stripped:"; ls -lh qbz-slint-linux-x86_64 | awk '{print $5}'
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: qbz-slint-linux-x86_64
+          path: qbz-slint-linux-x86_64
+          if-no-files-found: error