Fix broken links: replace /discussions with /issues and update task-manager reference

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

content/blog/metadata-driven-architecture.mdx

@@ -584,4 +584,4 @@ ObjectStack is our answer.
 
 ---
 
-*Want to dive deeper? Explore our [technical specifications](/docs/specifications) or join the discussion on [GitHub](https://github.com/objectstack-ai/spec/discussions).*
+*Want to dive deeper? Explore our [technical specifications](/docs/specifications) or join the discussion on [GitHub](https://github.com/objectstack-ai/spec/issues).*

content/blog/protocol-first-development.mdx

@@ -849,4 +849,4 @@ Join us in building it.
 
 ---
 
-*Ready to build on ObjectStack? Check out our [Getting Started Guide](/docs/guides/getting-started) or join the conversation on [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions).*
+*Ready to build on ObjectStack? Check out our [Getting Started Guide](/docs/guides/getting-started) or join the conversation on [GitHub Issues](https://github.com/objectstack-ai/spec/issues).*

content/docs/faq.mdx

@@ -307,6 +307,6 @@ Field.lookup({
 ## Still Have Questions?
 
 - 📖 Check the [Guides](/docs/guides/getting-started)
-- 💬 Ask in [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions)
+- 💬 Ask in [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 - 🐛 Report bugs in [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 - 📧 Email: support@objectstack.dev (for urgent issues)

content/docs/quick-start/build-first-app.mdx

@@ -363,5 +363,5 @@ All schemas are validated at build time using Zod. Check the error message for w
 
 ## Full Code
 
-The complete source code for this tutorial is available at:
-- [GitHub: examples/task-manager](https://github.com/objectstack-ai/spec/tree/main/examples/task-manager)
+The complete source code for a similar example is available at:
+- [GitHub: examples/todo](https://github.com/objectstack-ai/spec/tree/main/examples/todo)

content/docs/specifications/index.mdx

@@ -226,7 +226,7 @@ Example:
 Want to propose changes or additions?
 
 1. **Read:** [Contributing Guide](https://github.com/objectstack-ai/spec/blob/main/CONTRIBUTING.md)
-2. **Discuss:** [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions)
+2. **Discuss:** [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 3. **Propose:** [Submit an RFC](https://github.com/objectstack-ai/spec/issues/new?template=rfc.md)
 
 ### RFC Process

content/docs/troubleshooting.mdx

@@ -485,7 +485,7 @@ If you're still stuck after trying these solutions:
    - [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 
 2. **Ask the community:**
-   - [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions)
+   - [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 
 3. **Report a bug:**
    - [Create a new issue](https://github.com/objectstack-ai/spec/issues/new)

content/docs/tutorials.mdx

@@ -126,12 +126,12 @@ Apply what you've learned to build your own application!
 ## Community Examples
 
 Check out community-contributed examples:
-- [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions)
+- [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 - [Example Gallery](https://github.com/objectstack-ai/spec/tree/main/examples)
 
 ## Get Help
 
 Stuck on a tutorial? 
 - Check the [Troubleshooting Guide](/docs/troubleshooting)
-- Ask in [GitHub Discussions](https://github.com/objectstack-ai/spec/discussions)
+- Ask in [GitHub Issues](https://github.com/objectstack-ai/spec/issues)
 - Review the [FAQ](/docs/faq)