fix server-ci: install only claude-code, set SDK path in contract test

Two regressions from the previous CI install:

- Installing opencode-ai globally in server-ci/server-tests caused
  opencode-agent.test.ts (gated on \`hasOpenCode\`) to start running
  for the first time and surface real but unrelated test breakage.
  Trim the install to claude-code, which is all that's needed for the
  Claude e2e tests that motivated the change.

- claude-agent.integration.test.ts's supportedModels test calls the
  SDK's \`query()\` directly (bypassing ClaudeAgentClient) and didn't
  pass \`pathToClaudeCodeExecutable\`. The 0.2.71 SDK had a bundled
  cli.js fallback; 0.2.133 doesn't, so on Ubuntu CI it tries the
  per-platform binary path (\`...claude-agent-sdk-linux-x64-musl/claude\`)
  which isn't installed via the \`claude-code\` global. Resolve the
  binary explicitly in the test and pass it as the SDK option.

.github/workflows/ci.yml

@@ -88,8 +88,8 @@ jobs:
       - name: Install dependencies
         run: npm install
 
-      - name: Install agent CLIs for provider tests
-        run: npm install -g @anthropic-ai/claude-code @openai/codex@0.105.0 opencode-ai
+      - name: Install Claude Code CLI for provider tests
+        run: npm install -g @anthropic-ai/claude-code
 
       - name: Build highlight dependency
         run: npm run build --workspace=@getpaseo/highlight

.github/workflows/server-ci.yml

@@ -36,8 +36,8 @@ jobs:
       - name: Install server dependencies
         run: npm install --workspace=@getpaseo/server --include-workspace-root
 
-      - name: Install agent CLIs for provider tests
-        run: npm install -g @anthropic-ai/claude-code @openai/codex@0.105.0 opencode-ai
+      - name: Install Claude Code CLI for provider tests
+        run: npm install -g @anthropic-ai/claude-code
 
       - name: Build highlight dependency
         run: npm run build --workspace=@getpaseo/highlight