ci: fix OpenCode CLI installation on Ubuntu

Remove broken caching for OpenCode binary and add explicit PATH
configuration to ensure opencode command is available on Ubuntu runners.
The cache wasn't properly restoring the binary to PATH.

.github/workflows/ci.yml

@@ -28,24 +28,20 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-bun-
       
-      - name: Cache OpenCode binary
-        id: cache-opencode
-        uses: actions/cache@v4
-        with:
-          path: ~/.bun/bin/opencode
-          key: ${{ runner.os }}-opencode-${{ hashFiles('.github/workflows/ci.yml') }}
-          restore-keys: |
-            ${{ runner.os }}-opencode-
-      
       - name: Install dependencies
         run: bun install
       
       - name: Install OpenCode CLI
-        if: steps.cache-opencode.outputs.cache-hit != 'true'
-        run: bun install -g opencode-ai
+        run: |
+          bun install -g opencode-ai
+          echo "$HOME/.bun/bin" >> $GITHUB_PATH
+        shell: bash
       
       - name: Verify OpenCode installation
-        run: opencode --version
+        run: |
+          export PATH="$HOME/.bun/bin:$PATH"
+          opencode --version
+        shell: bash
       
       - name: Type check
         run: bun run tsc -noEmit -skipLibCheck