ci: run backend tests under cargo-nextest and cache deps with rust-cache

- Backend tests run with `cargo nextest run --profile ci`: one process
  per test, a 180s per-test timeout (src-tauri/.config/nextest.toml),
  and no fail-fast. The WSL2 nightly uses it too, still one test at a
  time and with the same selection as the old `--skip database::`, so a
  hung test is killed instead of eating the whole job.
- Integration tests shared one fixed test home, and each process wiped
  it on startup. Under nextest they ran concurrently and failed en
  masse, so tests/support.rs now picks a directory per
  NEXTEST_TEST_GLOBAL_SLOT. Plain `cargo test` keeps the old directory.
- Swatinem/rust-cache replaces the hand-rolled actions/cache step. It
  caches dependencies only, not the cc-switch crate that is rebuilt
  every run, and keys on OS, rustc version and Cargo.lock. The WSL2 CI
  job and the nightly share the `backend` key but only restore it, so
  their lib-only builds never save over the full Windows cache.
- Quote the $GITHUB_OUTPUT redirect that shellcheck flagged.

.github/workflows/ci.yml

@@ -78,7 +78,7 @@ jobs:
       - name: Get pnpm store directory
         id: pnpm-store
         shell: bash
-        run: echo "path=$(pnpm store path --silent)" >> $GITHUB_OUTPUT
+        run: echo "path=$(pnpm store path --silent)" >> "$GITHUB_OUTPUT"
 
       - name: Cache pnpm store
         uses: actions/cache@v5
@@ -142,15 +142,18 @@ jobs:
           sudo apt-get install -y --no-install-recommends libsoup-3.0-dev \
             || sudo apt-get install -y --no-install-recommends libsoup2.4-dev
 
-      - name: Cache Cargo registry and build
-        uses: actions/cache@v5
+      # 只缓存依赖：本仓库的 crate 每次都要重编，缓存它只会让缓存变大、恢复变慢。
+      # key 自带 OS、rustc 版本和 Cargo.lock；shared-key 让 WSL2 job 能读到 Windows 这份。
+      - name: Cache Rust dependencies
+        uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            src-tauri/target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
-          restore-keys: ${{ runner.os }}-cargo-
+          workspaces: src-tauri -> target
+          shared-key: backend
+
+      - name: Install cargo-nextest
+        uses: taiki-e/install-action@e407f7bafb71fd004bc5c2da3032e5470cbb6ef0 # v2.87.24
+        with:
+          tool: cargo-nextest
 
       - name: Create frontend dist placeholder
         shell: bash
@@ -162,8 +165,10 @@ jobs:
       - name: Clippy
         run: cargo clippy --manifest-path src-tauri/Cargo.toml -- -D warnings
 
+      # 每个测试一个进程，单测超时见 src-tauri/.config/nextest.toml。doctest 目前只有两个
+      # ignored，nextest 不跑 doctest 也不漏。
       - name: Run tests
-        run: cargo test --manifest-path src-tauri/Cargo.toml
+        run: cargo nextest run --manifest-path src-tauri/Cargo.toml --profile ci
 
   backend-windows-wsl2:
     name: Backend Checks (Windows + WSL2 home)
@@ -196,15 +201,14 @@ jobs:
           distribution: Ubuntu-24.04
           wsl-version: 2
 
-      - name: Cache Cargo registry and build
-        uses: actions/cache@v5
+      # 只恢复不保存：这里只编 lib 测试，若由它先存，同 key 的 Windows 缓存就只剩一小半。
+      # 完整缓存由 backend 矩阵的 Windows job 保存（同一个 shared-key）。
+      - name: Restore Rust dependencies
+        uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            src-tauri/target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
-          restore-keys: ${{ runner.os }}-cargo-
+          workspaces: src-tauri -> target
+          shared-key: backend
+          save-if: false
 
       - name: Create frontend dist placeholder
         shell: bash

.github/workflows/wsl2-nightly.yml

@@ -9,7 +9,9 @@ name: WSL2 Nightly
 # CC Switch skips Codex state DBs on WSL paths. So here
 # `database::` tests are skipped by name, tests that build SQLite fixtures skip
 # themselves (config::sqlite_unsupported_in_temp_dir), and integration tests,
-# which all create the app database, are not run.
+# which all create the app database, are not run. Tests run under cargo-nextest
+# one at a time, so a hung test is killed by the per-test timeout in
+# src-tauri/.config/nextest.toml instead of eating the whole job.
 on:
   schedule:
     - cron: "23 18 * * *" # 02:23 Beijing time
@@ -46,15 +48,19 @@ jobs:
           distribution: Ubuntu-24.04
           wsl-version: 2
 
-      - name: Cache Cargo registry and build
-        uses: actions/cache@v5
+      # 只恢复不保存：夜间只编 lib 测试，若由它存进 main 的缓存，PR 的 Windows job 会精确命中
+      # 这份不完整的缓存。完整缓存由 ci.yml backend 矩阵的 Windows job 保存（同一个 shared-key）。
+      - name: Restore Rust dependencies
+        uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            src-tauri/target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('src-tauri/Cargo.lock') }}
-          restore-keys: ${{ runner.os }}-cargo-
+          workspaces: src-tauri -> target
+          shared-key: backend
+          save-if: false
+
+      - name: Install cargo-nextest
+        uses: taiki-e/install-action@e407f7bafb71fd004bc5c2da3032e5470cbb6ef0 # v2.87.24
+        with:
+          tool: cargo-nextest
 
       - name: Create frontend dist placeholder
         shell: bash
@@ -104,4 +110,4 @@ jobs:
         run: |
           $env:TEMP = $env:CC_SWITCH_WSL_TEST_TEMP
           $env:TMP = $env:CC_SWITCH_WSL_TEST_TEMP
-          cargo test --lib --manifest-path src-tauri/Cargo.toml -- --test-threads=1 --skip database::
+          cargo nextest run --lib --manifest-path src-tauri/Cargo.toml --profile ci --test-threads 1 -E 'not test(/database::/)'