docs + devcontainer: fix scaffolding step, Azure AD rename, and Codespaces launch speedup

.devcontainer/Dockerfile

@@ -3,25 +3,15 @@
 # [Choice] Python version (use -bullseye variants on local arm64/Apple Silicon): 3, 3.10, 3.9, 3.8, 3.7, 3.6, 3-bullseye, 3.10-bullseye, 3.9-bullseye, 3.8-bullseye, 3.7-bullseye, 3.6-bullseye, 3-buster, 3.10-buster, 3.9-buster, 3.8-buster, 3.7-buster, 3.6-buster
 ARG VARIANT="3.12-bullseye"
 FROM mcr.microsoft.com/vscode/devcontainers/python:1-${VARIANT}
-# Set environment variables
+
 ENV DEBIAN_FRONTEND=noninteractive
 
-# Install system dependencies
-# The base image includes a Yarn APT source with an untrusted/expired GPG key; removing it prevents `apt-get update` from failing.
-RUN rm -f /etc/apt/sources.list.d/yarn.list \
-    && apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    build-essential \
-    wget \
-    && apt-get clean && rm -rf /var/lib/apt/lists/*
+# The base image includes a Yarn APT source with an untrusted/expired GPG key;
+# removing it prevents `apt-get update` from failing. .NET is now installed via
+# devcontainer features (see devcontainer.json) which are cached by Codespaces
+# across rebuilds — so no wget / dotnet-install.sh needed at image-build time.
+RUN rm -f /etc/apt/sources.list.d/yarn.list
 
-# Install .NET 10 SDK
-RUN wget https://dot.net/v1/dotnet-install.sh -O dotnet-install.sh \
-    && chmod +x dotnet-install.sh \
-    && ./dotnet-install.sh --channel 10.0 --install-dir /usr/share/dotnet \
-    && rm dotnet-install.sh \
-    && ln -s /usr/share/dotnet/dotnet /usr/bin/dotnet 
-
 # Define the path to the virtualenv to work with
 ARG VENV_PATH="/home/vscode/venv"
 

.devcontainer/devcontainer.json

@@ -2,49 +2,47 @@
 // README at: https://github.com/devcontainers/templates/tree/main/src/python
 {
 	"name": "Python 3",
-	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
 	"build": {
 		"dockerfile": "Dockerfile",
 		"context": "..",
 		"args": {
-		  "VARIANT": "3.12-bullseye"
+			"VARIANT": "3.12-bullseye"
 		}
-	  },
-	// Features to add to the dev container. More info: https://containers.dev/features.
-	// "features": {},
-
-	// Use 'forwardPorts' to make a list of ports inside the container available locally.
-	// "forwardPorts": [],
-
-	// Use 'postCreateCommand' to run commands after the container is created.
-	// "postCreateCommand": "",
-
-	// Configure tool-specific properties.
+	},
+	// .NET is installed via devcontainer feature rather than wget + shell install
+	// in the Dockerfile. Features are cached by the Codespaces infra across
+	// rebuilds and are baked into prebuilt images — massive cold-start win
+	// for conference wifi.
+	"features": {
+		"ghcr.io/devcontainers/features/dotnet:2": {
+			"version": "10.0"
+		}
+	},
+	// Pre-restore NuGet packages (Swashbuckle etc.) during container creation
+	// so attendees' first `dotnet run` doesn't wait on a cold restore.
+	"onCreateCommand": "cd /workspaces/${localWorkspaceFolderBasename}/src/csharp-app-complete && dotnet restore",
 	"customizations": {
 		"codespaces": {
 			"openFiles": [
-			  "src/python-app/webapp/main.py",
-			  "README.md"
+				"src/python-app/webapp/main.py",
+				"README.md"
 			]
 		},
 		"vscode": {
 			"settings": {
-			  "python.defaultInterpreterPath": "/home/vscode/venv/bin/python",
-			  "python.terminal.activateEnvInCurrentTerminal": true,
-			  "workbench.editorAssociations": {
-			    "*.md": "vscode.markdown.preview.editor"
-			  }
+				"python.defaultInterpreterPath": "/home/vscode/venv/bin/python",
+				"python.terminal.activateEnvInCurrentTerminal": true,
+				"workbench.editorAssociations": {
+					"*.md": "vscode.markdown.preview.editor"
+				}
 			},
 			"extensions": [
-			  "ms-python.python",
-			  "ms-python.vscode-pylance",
-			  "ms-dotnettools.csharp",
-			  "ms-dotnettools.csdevkit",
-			  "GitHub.copilot"
+				"ms-python.python",
+				"ms-python.vscode-pylance",
+				"ms-dotnettools.csharp",
+				"ms-dotnettools.csdevkit",
+				"GitHub.copilot"
 			]
 		}
 	}
-
-	// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
-	// "remoteUser": "root"
 }

.github/workflows/codespaces-prebuilds.yml

@@ -0,0 +1,30 @@
+name: "Codespaces Prebuilds"
+
+# Triggers GitHub Codespaces to build a prebuild image on push to main and
+# whenever the devcontainer config changes. Prebuilt images bake the devcontainer
+# features (.NET, Python deps) into a cached image, so attendees launching a
+# Codespace get a warm container in ~30 seconds instead of a 5-10 minute cold
+# build — critical for workshops on conference wifi.
+#
+# NOTE: This workflow only defines the schedule. Prebuilds must also be enabled
+# in the repository Settings → Codespaces → Set up prebuild. Once enabled, this
+# file ensures they refresh on the right triggers.
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - ".devcontainer/**"
+      - ".github/workflows/codespaces-prebuilds.yml"
+      - "src/python-app/requirements.txt"
+  workflow_dispatch:
+
+jobs:
+  notify:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Prebuild marker
+        run: |
+          echo "Devcontainer changed — Codespaces will refresh the prebuild."
+          echo "Actual prebuild runs on GitHub's Codespaces infrastructure, not in this job."

docs/en/create-csharp-scaffolding.md

@@ -2,9 +2,12 @@
 
 > *You should use GitHub Copilot in Agent Mode for this step and onwards.*
 
-Now that you have a good understanding of the project and its tests, you can start creating the C# scaffolding. You will start by creating a special file with instructions. This file is called *Copilot Instructions* and it should live in the [.github\instructions] folder. We've pre-created an empty file for you so all that is needed is to fill it out with new instructions.
+Now that you have a good understanding of the project and its tests, you can start creating the C# scaffolding. You will start by customising the repository-wide *Copilot Instructions* file, which lives at `.github/copilot-instructions.md` in the root of the repository. This file has been pre-populated with Python-focused guidance, and you will replace its contents with C#-focused instructions for the migration ahead.
 
-For this step, open the `.github\instructions\instructions.md` file and add the following:
+!!! note "`.github/copilot-instructions.md` vs `.github/instructions/`"
+    `.github/copilot-instructions.md` is the single repository-wide instructions file that Copilot loads for every chat in this repo. The `.github/instructions/` folder is a different mechanism — it holds multiple glob-scoped files (with `applyTo` frontmatter) that only activate when you edit matching paths. Those files are already populated and should not be edited for this step.
+
+For this step, open `.github/copilot-instructions.md` and **replace its entire contents** with the following:
 
 ```markdown
 # C# .NET 10 WebApi Migration Instructions

docs/en/workshop-introduction.md

@@ -15,7 +15,7 @@ This workshop will guide you through a realistic migration scenario using GitHub
     **Why did Zava choose C# for this migration?**
 
     - Easier integration with Zava's existing C# backend and internal tooling after the acquisition, reducing integration friction and time-to-market
-    - First-class Azure ecosystem support (Application Insights, Azure AD integration, IaC tooling) for enterprise deployments
+    - First-class Azure ecosystem support (Application Insights, Microsoft Entra ID integration, IaC tooling) for enterprise deployments
     - Strong enterprise tooling (Visual Studio, JetBrains Rider, .NET analyzers) that improves developer productivity, debugging and refactoring at scale
 
     **Why incremental validation matters in production:**
@@ -43,7 +43,7 @@ You will be working with a Python project (representing an acquired service) tha
 
 Zava enforces a set of enterprise standards for services running in production. Below are the key standards and how migrating to C#/.NET helps meet them more effectively than the current Python-based implementation:
 
-- Security and identity: .NET has mature libraries for secure authentication/authorization (Azure AD integration, token validation, strong cryptography libraries) and a robust ecosystem of security scanning and policy enforcement tools.
+- Security and identity: .NET has mature libraries for secure authentication/authorization (Microsoft Entra ID integration, token validation, strong cryptography libraries) and a robust ecosystem of security scanning and policy enforcement tools.
 - Observability and diagnostics: Deep integration with Application Insights, structured logging (ILogger), distributed tracing, and first-class telemetry SDKs make it easier to meet Zava's observability SLAs.
 - Reliability and performance: Strong concurrency primitives, the .NET runtime optimizations, and optional ahead-of-time compilation reduce latency and improve throughput for enterprise load patterns.
 - Maintainability and governance: Static typing, Roslyn analyzers, standardized NuGet package management, and enforced code quality checks help Zava keep a consistent, auditable codebase across teams.

docs/ja/create-csharp-scaffolding.md

@@ -2,9 +2,12 @@
 
 > *このステップ以降は GitHub Copilot の Agent モードを使います。*
 
-プロジェクトとテストの全体像を把握できたら、C# プロジェクト雛形の作成に進みましょう。まず最初に、インストラクション用の特別なファイルを作成します。このファイルは *Copilot Instructions* と呼ばれ、`.github\instructions` フォルダに置きます。空のファイルがあらかじめ用意されているので、以下の指示内容を書き込むだけでOKです。
+プロジェクトとテストの全体像を把握できたら、C# プロジェクト雛形の作成に進みましょう。まず最初に、リポジトリ全体に適用される *Copilot Instructions* ファイルをカスタマイズします。このファイルはリポジトリのルートにある `.github/copilot-instructions.md` です。現在は Python に関する内容で事前設定されているので、これから行う C# 移行に向けた内容に**全体を置き換えます**。
 
-`.github\instructions\instructions.md` ファイルを開き、以下の内容を追記してください:
+!!! note "`.github/copilot-instructions.md` と `.github/instructions/` の違い"
+    `.github/copilot-instructions.md` はリポジトリ全体で使われる単一の Copilot インストラクションファイルで、このリポジトリ内のすべてのチャットで自動的に読み込まれます。一方 `.github/instructions/` フォルダは別の仕組みで、`applyTo` フロントマターで指定されたパスを編集するときだけ有効になる、glob スコープ付きの複数のファイルを置くためのものです。これらのファイルは既に内容が入っており、このステップでは編集する必要はありません。
+
+`.github/copilot-instructions.md` を開き、**ファイルの内容をすべて以下で置き換えてください**:
 
 ```markdown
 # C# .NET 10 WebApi Migration Instructions

docs/ja/workshop-introduction.md

@@ -15,7 +15,7 @@ Zava は最近、Python でアプリ開発をしている企業を買収しま
     **Zava が C# を選んだ理由**
 
     - 買収後の既存 C# バックエンドや社内ツールとの統合が容易になり、統合コストと市場投入までの時間を短縮できる
-    - Azure エコシステムとの深い統合 (Application Insights・Azure AD・IaC ツール群) によりエンタープライズデプロイが確実になる
+    - Azure エコシステムとの深い統合 (Application Insights・Microsoft Entra ID・IaC ツール群) によりエンタープライズデプロイが確実になる
     - Visual Studio・JetBrains Rider・.NET アナライザーなどの豊富なツール群により、開発生産性とリファクタリング・デバッグ効率が大規模でも維持される
 
     **本番環境で段階的な検証が重要な理由**
@@ -42,7 +42,7 @@ Python プロジェクト（買収したサービスを想定）を使って作
 
 Zava は本番環境で稼働するサービスに対して、一連のエンタープライズ標準を定めています。以下の主要な標準と、C#/.NET への移行がそれぞれの標準をより効果的に満たす理由を示します。
 
-- セキュリティとアイデンティティ: .NET には安全な認証・認可のための成熟したライブラリ (Azure AD 統合・トークン検証・強力な暗号化ライブラリ) と堅牢なセキュリティスキャン・ポリシー適用ツールのエコシステムがある
+- セキュリティとアイデンティティ: .NET には安全な認証・認可のための成熟したライブラリ (Microsoft Entra ID 統合・トークン検証・強力な暗号化ライブラリ) と堅牢なセキュリティスキャン・ポリシー適用ツールのエコシステムがある
 - オブザーバビリティと診断: Application Insights との深い統合・構造化ログ (ILogger)・分散トレーシング・ファーストクラスのテレメトリ SDK により、Zava のオブザーバビリティ SLA を満たしやすい
 - 信頼性とパフォーマンス: 強力な並行処理プリミティブ・.NET ランタイムの最適化・オプションの AOT コンパイルにより、エンタープライズ負荷パターンでのレイテンシ削減とスループット向上を実現する
 - 保守性とガバナンス: 静的型付け・Roslyn アナライザー・標準化された NuGet パッケージ管理・コード品質チェックの自動適用により、チーム全体で一貫した監査可能なコードベースを維持できる