fix: Use explicit type exports for Bun compatibility

TypeScript interfaces (GitHubRepo, SyncResult, SyncProgress) were being
re-exported as values, which fails in Bun since types are erased at
runtime. Changed to use `export type` for type-only exports.

Also added a guideline to AGENTS.md to prevent this issue in the future.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dcramer

AGENTS.md

@@ -54,6 +54,19 @@ When adding or modifying CLI commands, update:
 - `src/cli/help.ts` — Built-in help text
 - `docs/src/pages/cli.astro` — CLI reference documentation
 
+## TypeScript Exports
+
+Use `export type` for type-only exports (interfaces, type aliases). Bun requires explicit type exports:
+
+```ts
+// Good
+export type { GitHubRepo } from "./remote.js";
+export { getGitHubRepo } from "./remote.js";
+
+// Bad - fails in Bun
+export { GitHubRepo, getGitHubRepo } from "./remote.js";
+```
+
 ## Testing
 
 When adding new behavior or modifying existing functionality, review `TESTING.md` to determine if tests are needed. Key points:

src/core/github/index.ts

@@ -2,19 +2,15 @@
 // Internal utilities should be imported directly from their source files
 
 export { getGitHubToken } from "./token.js";
+export type { GitHubRepo } from "./remote.js";
 export {
-  GitHubRepo,
   getGitRemoteUrl,
   parseGitHubUrl,
   getGitHubRepo,
   parseGitHubIssueRef,
 } from "./remote.js";
-export {
-  GitHubSyncService,
-  SyncResult,
-  SyncProgress,
-  getGitHubIssueNumber,
-} from "./sync.js";
+export type { SyncResult, SyncProgress } from "./sync.js";
+export { GitHubSyncService, getGitHubIssueNumber } from "./sync.js";
 export {
   createGitHubSyncService,
   createGitHubSyncServiceOrThrow,