ci: switch from self-hosted to macos-15 GitHub runners

Mac mini disk/CPU is saturated with 10+ concurrent PR builds.
Temporarily switching to GitHub-hosted macos-15 runners until we have
more disk space. Self-hosted was faster due to incremental Rust builds
but was causing CI queue buildup and false test failures.

Changes:
- CI: self-hosted → macos-15
- Release build: self-hosted → macos-15
- Remove per-runner pnpm store isolation (not needed on GitHub runners)
- Add Rust cache for GitHub runners (keyed by Cargo.lock)
- Remove CARGO_INCREMENTAL=1 (managed via cache instead)

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ on:
 jobs:
   test:
     name: Tests & Quality Checks
-    runs-on: self-hosted
+    runs-on: macos-15
 
     steps:
       - uses: actions/checkout@v4
@@ -39,16 +39,13 @@ jobs:
             ~/.cargo/registry
             ~/.cargo/git
             src-tauri/target
-          key: ${{ runner.os }}-${{ runner.name }}-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
+          key: ${{ runner.os }}-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
           restore-keys: |
-            ${{ runner.os }}-${{ runner.name }}-cargo-
+            ${{ runner.os }}-cargo-
 
       - name: Install cargo-llvm-cov
         uses: taiki-e/install-action@cargo-llvm-cov
 
-      - name: Configure pnpm store (per-runner isolation)
-        run: pnpm config set store-dir "$HOME/.pnpm-store-${{ runner.name }}"
-
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 

.github/workflows/release.yml

@@ -34,7 +34,7 @@ jobs:
   build:
     name: Build (${{ matrix.arch }})
     needs: version
-    runs-on: self-hosted
+    runs-on: macos-15
     strategy:
       fail-fast: true
       matrix:
@@ -60,8 +60,16 @@ jobs:
         with:
           targets: ${{ matrix.target }}
 
-      # Self-hosted runner: cargo registry + target dir persist on disk between runs.
-      # No need for Swatinem/rust-cache — incremental builds kick in automatically.
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            src-tauri/target
+          key: ${{ runner.os }}-release-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-release-cargo-
 
       - name: Install frontend dependencies
         run: pnpm install --frozen-lockfile
@@ -76,8 +84,6 @@ jobs:
         env:
           TAURI_SIGNING_PRIVATE_KEY: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY }}
           TAURI_SIGNING_PRIVATE_KEY_PASSWORD: ""
-          # Incremental compilation — reuses previous build artifacts on self-hosted runner
-          CARGO_INCREMENTAL: "1"
         run: |
           pnpm tauri build --target ${{ matrix.target }}