ci(zephyr-e2e): avoid disk exhaustion on GitHub runners

- Remove dotnet/android/boost images to free space
- Build rsgdb in debug (no release LTO) and set RSGDB to target/debug/rsgdb
- Build rsgdb before west update so peak usage is lower
- Document debug binary in CONTRIBUTING

Made-with: Cursor

Author: Alex J Lennon

.github/workflows/zephyr-e2e.yml

@@ -40,6 +40,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # Runners are ~14GB; Zephyr west tree + SDK + release+LTO can exhaust disk.
+      - name: Free disk space (remove unused CI images)
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /usr/local/share/boost
+          df -h
+
       - name: Install host packages (Zephyr host + gdb stack)
         run: |
           sudo apt-get update
@@ -65,6 +71,12 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
 
+      # Debug build only: release profile uses LTO + huge rmeta intermediates and fills the disk.
+      - name: Build rsgdb (debug)
+        env:
+          CARGO_INCREMENTAL: "0"
+        run: cargo build --verbose
+
       - name: Cache Zephyr SDK
         id: zephyr-sdk-cache
         uses: actions/cache@v4
@@ -103,8 +115,7 @@ jobs:
           fi
           west update
 
-      - name: Build rsgdb (release)
-        run: cargo build --release --verbose
-
       - name: Run Zephyr native_sim E2E
+        env:
+          RSGDB: ${{ github.workspace }}/target/debug/rsgdb
         run: ./scripts/e2e_zephyr_native_sim.sh

CONTRIBUTING.md

@@ -101,7 +101,7 @@ RUN_E2E_ZEPHYR_NATIVE=1 ./scripts/validate_local.sh
 ### GitHub Actions (optional E2E parity)
 
 - **GDB smoke** — the **CI** workflow includes an Ubuntu job that runs `scripts/e2e_gdb_smoke.sh` after `cargo build --release` (same idea as `RUN_E2E_GDB=1` with `validate_local.sh`, without duplicating fmt/clippy/doc in that job).
-- **Zephyr `native_sim`** — the **Zephyr E2E** workflow (`.github/workflows/zephyr-e2e.yml`) provisions a cached west workspace, then runs `scripts/e2e_zephyr_native_sim.sh`. It runs when `scripts/e2e_zephyr_native_sim.sh` or `scripts/zephyr_multi_printf_app/` change, on pushes to `main`/`develop` for those paths, on a weekly schedule, and via **workflow_dispatch** (Actions → Zephyr E2E → Run workflow). This mirrors `RUN_E2E_ZEPHYR_NATIVE=1` locally without checking a Zephyr tree into this repo.
+- **Zephyr `native_sim`** — the **Zephyr E2E** workflow (`.github/workflows/zephyr-e2e.yml`) provisions a cached west workspace, then runs `scripts/e2e_zephyr_native_sim.sh`. It runs when `scripts/e2e_zephyr_native_sim.sh` or `scripts/zephyr_multi_printf_app/` change, on pushes to `main`/`develop` for those paths, on a weekly schedule, and via **workflow_dispatch** (Actions → Zephyr E2E → Run workflow). This mirrors `RUN_E2E_ZEPHYR_NATIVE=1` locally without checking a Zephyr tree into this repo. The workflow builds **`target/debug/rsgdb`** (not release) and frees some preinstalled SDKs on the runner so the job fits on the GitHub-hosted disk.
 
 ### Issue tracking