feat: Copy project subagents to Claude runtime environment

Enables custom subagents defined in .claude/agents/ to work in GitHub Actions by:
- Checking for project agents in GITHUB_WORKSPACE/.claude/agents/
- Creating ~/.claude/agents/ directory if needed
- Copying all .md agent files to Claude's runtime location
- Following same pattern as slash commands for consistency

Includes comprehensive test coverage for the new functionality.

base-action/src/setup-claude-code-settings.ts

@@ -79,4 +79,31 @@ export async function setupClaudeCodeSettings(
       console.log(`Slash commands directory not found or error copying: ${e}`);
     }
   }
+
+  // Copy project subagents to Claude's agents directory
+  // Use GITHUB_WORKSPACE if available (set by GitHub Actions), otherwise use current directory
+  const workspaceDir = process.env.GITHUB_WORKSPACE || process.cwd();
+  const projectAgentsDir = `${workspaceDir}/.claude/agents`;
+  const claudeAgentsDir = `${home}/.claude/agents`;
+
+  try {
+    await $`test -d ${projectAgentsDir}`.quiet();
+    console.log(`Found project agents directory at ${projectAgentsDir}`);
+
+    // Ensure target agents directory exists
+    await $`mkdir -p ${claudeAgentsDir}`.quiet();
+
+    // Copy all .md files from project agents to Claude's agents directory
+    await $`cp ${projectAgentsDir}/*.md ${claudeAgentsDir}/ 2>/dev/null || true`.quiet();
+
+    // Count copied agents for logging
+    const agentFiles = await $`ls ${claudeAgentsDir}/*.md 2>/dev/null | wc -l`
+      .quiet()
+      .text();
+    const agentCount = parseInt(agentFiles.trim()) || 0;
+    console.log(`Copied ${agentCount} agent(s) to ${claudeAgentsDir}`);
+  } catch (e) {
+    // Directory doesn't exist or no agents to copy - this is expected in most cases
+    console.log(`No project agents directory found at ${projectAgentsDir}`);
+  }
 }

base-action/test/setup-claude-code-settings.test.ts

@@ -215,4 +215,70 @@ describe("setupClaudeCodeSettings", () => {
     const settingsContent = await readFile(settingsPath, "utf-8");
     expect(JSON.parse(settingsContent).enableAllProjectMcpServers).toBe(true);
   });
+
+  test("should copy project agents when .claude/agents directory exists", async () => {
+    // Create a mock project structure with agents
+    const projectDir = join(testHomeDir, "test-project");
+    const projectAgentsDir = join(projectDir, ".claude", "agents");
+    await mkdir(projectAgentsDir, { recursive: true });
+    
+    // Create test agent files
+    await writeFile(
+      join(projectAgentsDir, "test-agent.md"),
+      "---\nname: test-agent\ndescription: Test agent\n---\nTest agent content",
+    );
+    await writeFile(
+      join(projectAgentsDir, "another-agent.md"),
+      "---\nname: another-agent\n---\nAnother agent",
+    );
+    
+    // Set GITHUB_WORKSPACE to the test project directory
+    const originalWorkspace = process.env.GITHUB_WORKSPACE;
+    process.env.GITHUB_WORKSPACE = projectDir;
+    
+    try {
+      await setupClaudeCodeSettings(undefined, testHomeDir);
+      
+      // Check that agents were copied
+      const agentsDir = join(testHomeDir, ".claude", "agents");
+      const files = await readdir(agentsDir);
+      expect(files).toContain("test-agent.md");
+      expect(files).toContain("another-agent.md");
+      
+      // Verify content was copied correctly
+      const content = await readFile(join(agentsDir, "test-agent.md"), "utf-8");
+      expect(content).toContain("Test agent content");
+    } finally {
+      // Restore original GITHUB_WORKSPACE
+      if (originalWorkspace !== undefined) {
+        process.env.GITHUB_WORKSPACE = originalWorkspace;
+      } else {
+        delete process.env.GITHUB_WORKSPACE;
+      }
+    }
+  });
+
+  test("should handle missing project agents directory gracefully", async () => {
+    // Set GITHUB_WORKSPACE to a directory without .claude/agents
+    const projectDir = join(testHomeDir, "project-without-agents");
+    await mkdir(projectDir, { recursive: true });
+    
+    const originalWorkspace = process.env.GITHUB_WORKSPACE;
+    process.env.GITHUB_WORKSPACE = projectDir;
+    
+    try {
+      await setupClaudeCodeSettings(undefined, testHomeDir);
+      
+      // Should complete without errors
+      const settingsContent = await readFile(settingsPath, "utf-8");
+      const settings = JSON.parse(settingsContent);
+      expect(settings.enableAllProjectMcpServers).toBe(true);
+    } finally {
+      if (originalWorkspace !== undefined) {
+        process.env.GITHUB_WORKSPACE = originalWorkspace;
+      } else {
+        delete process.env.GITHUB_WORKSPACE;
+      }
+    }
+  });
 });