ci: enable CI workflows on push/PR

Enable CI on push to main and pull requests, matching the
zentinel proxy CI pattern. Updates actions to checkout@v6,
rust-toolchain@stable, cache@v5 with separate registry and
build caches, free disk space steps, and concurrency control.

Author: raffaelschneider

.github/workflows/ci.yml

@@ -1,70 +1,99 @@
-# CI workflow for zentinel-agent-sdk
-# All jobs are disabled (if: false) to conserve GHA minutes.
-# To enable: change `if: false` to `if: true` and uncomment triggers.
-
 name: CI
 
 on:
-  workflow_dispatch:
-  # Uncomment to enable on push/PR:
-  # push:
-  #   branches: [main]
-  # pull_request:
-  #   branches: [main]
+  push:
+    branches: [main]
+  pull_request:
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
 
 env:
   CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
 
 jobs:
-  check:
-    name: Check
-    runs-on: ubuntu-latest
-    if: false  # Disabled - change to true to enable
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-      - run: cargo check --all-features
-
-  test:
-    name: Test
-    runs-on: ubuntu-latest
-    if: false  # Disabled - change to true to enable
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-      - run: cargo test --all-features
-
   fmt:
-    name: Format
+    name: Formatting
     runs-on: ubuntu-latest
-    if: false  # Disabled - change to true to enable
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt
-      - run: cargo fmt --all -- --check
+      - run: cargo fmt --all --check
 
   clippy:
     name: Clippy
     runs-on: ubuntu-latest
-    if: false  # Disabled - change to true to enable
     steps:
-      - uses: actions/checkout@v4
+      - name: Free disk space
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache/CodeQL
+          sudo docker image prune --all --force
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
-      - uses: Swatinem/rust-cache@v2
-      - run: cargo clippy --all-features -- -D warnings
+      - uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-registry-
+      - uses: actions/cache@v5
+        with:
+          path: target
+          key: ${{ runner.os }}-cargo-clippy-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-clippy-
+      - run: cargo clippy --workspace --all-targets -- -D warnings
+
+  test:
+    name: Tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: Free disk space
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache/CodeQL
+          sudo docker image prune --all --force
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-registry-
+      - uses: actions/cache@v5
+        with:
+          path: target
+          key: ${{ runner.os }}-cargo-test-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-test-
+      - run: cargo test --workspace
 
   examples:
-    name: Check Examples
+    name: Examples
     runs-on: ubuntu-latest
-    if: false  # Disabled - change to true to enable
     steps:
-      - uses: actions/checkout@v4
+      - name: Free disk space
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc /opt/hostedtoolcache/CodeQL
+          sudo docker image prune --all --force
+      - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
+      - uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+          key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-registry-
+      - uses: actions/cache@v5
+        with:
+          path: target
+          key: ${{ runner.os }}-cargo-examples-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-examples-
       - run: cargo check --examples