docs: update Learning Hub for CLI v1.0.10/v1.0.11 features (#1150)

- Add monorepo support section to copilot-configuration-basics:
  customizations discovered at every directory level up to git root
- Add personal skills directory (~/.agents/skills/) documentation
- Add /clear vs /new session command distinction + /undo command
- Add MCP organization policy enforcement to understanding-mcp-servers
- Add sessionStart additionalContext injection to automating-with-hooks
- Add extension hooks merging behaviour to automating-with-hooks

Source: https://github.com/github/copilot-cli/releases/tag/v1.0.11
Source: https://github.com/github/copilot-cli/releases/tag/v1.0.10

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

website/src/content/docs/learning-hub/automating-with-hooks.md

@@ -3,7 +3,7 @@ title: 'Automating with Hooks'
 description: 'Learn how to use hooks to automate lifecycle events like formatting, linting, and governance checks during Copilot agent sessions.'
 authors:
   - GitHub Copilot Learning Hub Team
-lastUpdated: 2026-03-22
+lastUpdated: 2026-03-24
 estimatedReadingTime: '8 minutes'
 tags:
   - hooks
@@ -99,6 +99,26 @@ Hooks can trigger on several lifecycle events:
 
 > **Key insight**: The `preToolUse` hook is the most powerful — it can **approve or deny** individual tool executions. This enables fine-grained security policies like blocking specific shell commands or requiring approval for sensitive file operations.
 
+### sessionStart additionalContext
+
+The `sessionStart` hook supports an `additionalContext` field in its output. When your hook script writes JSON to stdout containing an `additionalContext` key, that text is **injected directly into the conversation** at the start of the session. This lets hooks dynamically provide environment-specific context—such as the current git branch, deployment environment, or team onboarding notes—without requiring the user to paste it manually.
+
+Example hook script that surfaces context:
+
+```bash
+#!/usr/bin/env bash
+# Output JSON with additionalContext to inject into the session
+cat <<EOF
+{
+  "additionalContext": "Current branch: $(git rev-parse --abbrev-ref HEAD). Open tickets: $(gh issue list --limit 3 --json number,title | jq -r '.[] | \"#\(.number) \(.title)\"' | tr '\n' '; ')"
+}
+EOF
+```
+
+### Extension Hooks Merging
+
+When multiple IDE extensions (or a mix of extensions and a `hooks.json` file) each define hooks, all hook definitions are **merged** rather than the last one overwriting the others. This means you can layer hooks from different sources—a project's `.github/hooks/` file, an extension you have installed, and a personal settings file—and all of them will fire for the relevant events.
+
 ### Cross-Platform Event Name Compatibility
 
 Hook event names can be written in **camelCase** (e.g., `preToolUse`) or **PascalCase** (e.g., `PreToolUse`). Both are accepted, making hook configuration files compatible across GitHub Copilot CLI, VS Code, and Claude Code without modification. Hooks also support Claude Code's nested `matcher`/`hooks` structure alongside the standard flat format.