docs: update cross-references and glossary for new articles

- Replace 'Building Custom Agents (coming soon)' with real links
- Add Hook and Coding Agent entries to the glossary
- Add MCP Servers learning hub link to glossary MCP entry

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

website/src/content/learning-hub/copilot-configuration-basics.md

@@ -382,4 +382,4 @@ Now that you understand Copilot configuration, explore how to create powerful cu
 - **[Understanding Copilot Context](../learning-hub/understanding-copilot-context/)** - Learn how configuration affects context usage
 - **[Defining Custom Instructions](../learning-hub/defining-custom-instructions/)** - Create persistent context for your projects
 - **[Creating Effective Skills](../learning-hub/creating-effective-skills/)** - Build reusable task folders with bundled assets
-- **Building Custom Agents** _(coming soon)_ - Develop specialized assistants
+- **[Building Custom Agents](../learning-hub/building-custom-agents/)** - Develop specialized assistants

website/src/content/learning-hub/creating-effective-skills.md

@@ -391,13 +391,13 @@ A: Yes, for clarity. Show examples of desired output format, patterns to follow,
 Now that you understand effective skills, you can:
 
 - **Explore Repository Examples**: Browse the [Skills Directory](../skills/) for production skills covering diverse workflows
-- **Learn About Agents**: Building Custom Agents _(coming soon)_ — When to upgrade from skills to full agents
+- **Learn About Agents**: [Building Custom Agents](../learning-hub/building-custom-agents/) — When to upgrade from skills to full agents
 - **Understand Instructions**: [Defining Custom Instructions](../learning-hub/defining-custom-instructions/) — Complement skills with automatic context
 - **Decision Framework**: Choosing the Right Customization _(coming soon)_ — When to use skills vs other types
 
 **Suggested Reading Order**:
 1. This article (creating effective skills)
-2. Building Custom Agents _(coming soon)_ — More sophisticated workflows
+2. [Building Custom Agents](../learning-hub/building-custom-agents/) — More sophisticated workflows
 3. Choosing the Right Customization _(coming soon)_ — Decision guidance
 
 ---

website/src/content/learning-hub/defining-custom-instructions.md

@@ -308,10 +308,10 @@ Now that you understand custom instructions, you can:
 
 - **Explore Repository Examples**: Browse [Instructions Directory](../instructions/) - Over 120 real-world examples covering frameworks, languages, and domains
 - **Learn About Skills**: [Creating Effective Skills](../learning-hub/creating-effective-skills/) - Discover when to use skills instead of instructions
-- **Understand Agents**: Building Custom Agents _(coming soon)_ - See how agents complement instructions for complex workflows
+- **Understand Agents**: [Building Custom Agents](../learning-hub/building-custom-agents/) - See how agents complement instructions for complex workflows
 - **Configuration Basics**: [Copilot Configuration Basics](../learning-hub/copilot-configuration-basics/) - Learn how to organize and manage your customizations
 
 **Suggested Reading Order**:
 1. This article (defining custom instructions)
 2. [Creating Effective Skills](../learning-hub/creating-effective-skills/) - Learn complementary customization type
-3. Choosing the Right Customization _(coming soon)_ - Decision framework for when to use each type
+3. [Building Custom Agents](../learning-hub/building-custom-agents/) - Decision framework for when to use each type

website/src/content/learning-hub/github-copilot-terminology-glossary.md

@@ -177,12 +177,44 @@ A standardized protocol for connecting AI assistants like GitHub Copilot to exte
 
 **Example**: An MCP server might provide access to your company's internal documentation, AWS resources, or a specific database system.
 
-**Learn more**: [Model Context Protocol](https://modelcontextprotocol.io/) | [MCP Specification](https://spec.modelcontextprotocol.io/)
+**Learn more**: [Model Context Protocol](https://modelcontextprotocol.io/) | [MCP Specification](https://spec.modelcontextprotocol.io/) | [Understanding MCP Servers](/learning-hub/understanding-mcp-servers/)
 
 **Related terms**: [Tools](#tools), [Built-in Tool](#built-in-tool)
 
 ---
 
+### Hook
+
+A shell command or script that runs automatically in response to lifecycle events during a Copilot agent session. Hooks are defined in a `hooks.json` file and can trigger on events like session start, prompt submission, or before a commit. They provide deterministic automation—linting, formatting, governance scanning—that doesn't depend on the AI remembering to do it.
+
+**Example**: A `copilotAgentCommit` hook that runs Prettier before every commit the agent makes.
+
+**When to use**: For deterministic automation that must happen reliably, like formatting code, running linters, or auditing prompts for compliance.
+
+**Learn more**: [Automating with Hooks](/learning-hub/automating-with-hooks/)
+
+**Related terms**: [Agent](#agent), [Coding Agent](#coding-agent)
+
+---
+
+### Coding Agent
+
+The autonomous GitHub Copilot agent that works on issues in a cloud environment without continuous human guidance. You assign an issue to Copilot, it spins up a dev environment, implements a solution, runs tests, and opens a pull request for review.
+
+**Key characteristics**:
+- Runs in an isolated cloud environment
+- Uses your repository's instructions, agents, skills, and hooks
+- Always produces a PR—it can't merge or deploy
+- Supports iteration via PR comments
+
+**When to use**: For well-defined tasks with clear acceptance criteria that can be completed autonomously.
+
+**Learn more**: [Using the Copilot Coding Agent](/learning-hub/using-copilot-coding-agent/)
+
+**Related terms**: [Agent](#agent), [Hook](#hook)
+
+---
+
 ### Tools
 
 Capabilities that GitHub Copilot can invoke to perform actions or retrieve information. Tools fall into two categories: