feat(KB-002): add interactive GitHub issue import

- Add --interactive (-i) flag to 'kb task import' CLI command for selective import
- Add GitHubImportModal component to dashboard with issue browser and selection
- Add /api/github/issues/fetch and /api/github/issues/import API endpoints
- Add kb_task_import_github_issue and kb_task_browse_github_issues tools to pi extension
- Add comprehensive tests for CLI, dashboard API, and UI components

packages/cli/src/__tests__/extension.test.ts

@@ -81,6 +81,8 @@ describe("kb pi extension", () => {
         "kb_task_pause",
         "kb_task_unpause",
         "kb_task_import_github",
+        "kb_task_import_github_issue",
+        "kb_task_browse_github_issues",
       ];
 
       for (const name of expected) {