fix(ci): checkout zentinel repo for agent-protocol path dependency

The agent-protocol crate is referenced as a path dependency pointing
to ../zentinel/crates/agent-protocol. CI and release workflows need
the zentinel repo checked out at the correct relative path.

Author: raffaelschneider

.github/workflows/ci.yml

@@ -18,6 +18,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Checkout zentinel (for agent-protocol path dep)
+        uses: actions/checkout@v4
+        with:
+          repository: zentinelproxy/zentinel
+          path: ../zentinel
+
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
 
@@ -46,6 +52,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Checkout zentinel (for agent-protocol path dep)
+        uses: actions/checkout@v4
+        with:
+          repository: zentinelproxy/zentinel
+          path: ../zentinel
+
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
 
@@ -88,6 +100,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Checkout zentinel (for agent-protocol path dep)
+        uses: actions/checkout@v4
+        with:
+          repository: zentinelproxy/zentinel
+          path: ../zentinel
+
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
         with:

.github/workflows/release.yml

@@ -40,6 +40,12 @@ jobs:
         with:
           path: agent
 
+      - name: Checkout zentinel (for agent-protocol path dep)
+        uses: actions/checkout@v4
+        with:
+          repository: zentinelproxy/zentinel
+          path: zentinel
+
       - name: Checkout SDK
         uses: actions/checkout@v4
         with: