chore: Add changeset and update dependencies

- Add changeset for OAuth provider API key fix
- Update bun.lock with devDependencies
- Fix formatting in issue-data.json

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: konard

.changeset/fix-oauth-provider-api-keys.md

@@ -0,0 +1,13 @@
+---
+'@link-assistant/agent': patch
+---
+
+fix: Use valid placeholder API keys for OAuth providers (Anthropic, GitHub Copilot, OpenAI)
+
+When using `--model anthropic/claude-sonnet-4-5` after authenticating with `agent auth login` (Anthropic > Claude Pro/Max), the command failed with `ProviderInitError` at line 732 in `src/provider/provider.ts`.
+
+The OAuth authentication plugin loaders in `src/auth/plugins.ts` were returning empty strings (`''`) for the `apiKey` parameter. The AI SDK providers (e.g., `@ai-sdk/anthropic`, `@ai-sdk/openai`) require a non-empty `apiKey` parameter even when using custom fetch functions for authentication. The empty string failed validation, causing provider initialization to fail.
+
+This fix changes the `apiKey` value from an empty string to a descriptive placeholder string (`'oauth-token-used-via-custom-fetch'`) for all OAuth loaders (AnthropicPlugin, GitHubCopilotPlugin, and OpenAIPlugin). The placeholder satisfies AI SDK validation requirements while the actual OAuth authentication happens via Bearer tokens in the custom fetch's Authorization header.
+
+Fixes #47