feat: migrate CLAUDE.md content to OpenSpec specs and initialize workflow

Move project description and tech stack research from CLAUDE.md into
openspec/specs/project/ and openspec/specs/stack/. Slim CLAUDE.md to a
pointer file. Populate config.yaml with project context. Add OpenSpec
CLI skills and commands.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/specs/chat-ui/spec.md

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+## Purpose
+
+Define the chat interface — message display, input handling, auto-scroll, and routing.
+
+## Requirements
+
+### Requirement: Message display
+
+The chat page SHALL display messages in a vertically scrolling list, with each message showing the sender role (user or assistant), the message content, and a visual distinction between user and assistant messages (e.g., alignment, color, or avatar).
+
+#### Scenario: User message displayed
+
+- **WHEN** the user sends a message
+- **THEN** the message appears in the message list aligned or styled to indicate it is from the user
+
+#### Scenario: Assistant message displayed
+
+- **WHEN** the assistant responds
+- **THEN** the response appears in the message list with distinct styling from user messages (different alignment, color, or avatar)
+
+#### Scenario: Message ordering
+
+- **WHEN** multiple messages exist in the conversation
+- **THEN** messages are displayed in chronological order, oldest at top
+
+### Requirement: Message input
+
+The chat page SHALL provide a text input area at the bottom of the page where the user can type and submit messages.
+
+#### Scenario: Submit via button
+
+- **WHEN** the user types text and clicks the send button
+- **THEN** the message is added to the conversation and the input is cleared
+
+#### Scenario: Submit via Enter key
+
+- **WHEN** the user types text and presses Enter
+- **THEN** the message is submitted (same as clicking send)
+
+#### Scenario: Empty input blocked
+
+- **WHEN** the user attempts to send an empty or whitespace-only message
+- **THEN** nothing is sent and no message is added
+
+### Requirement: Hardcoded response
+
+In this phase, the assistant SHALL reply with a hardcoded message to every user input. This stubs the AI integration point for future phases.
+
+#### Scenario: Bot replies to any input
+
+- **WHEN** the user sends any message
+- **THEN** the assistant replies with a hardcoded response (e.g., "This is a placeholder response. AI integration coming soon!")
+
+### Requirement: Auto-scroll
+
+The message list SHALL automatically scroll to the newest message when a new message is added.
+
+#### Scenario: New message scrolls into view
+
+- **WHEN** a new message (user or assistant) is added to the conversation
+- **THEN** the message list scrolls to the bottom so the new message is visible
+
+### Requirement: Chat page is default route
+
+The chat page SHALL be the default route (`/`) of the application.
+
+#### Scenario: App opens to chat
+
+- **WHEN** the user navigates to the root URL
+- **THEN** the chat page is displayed

openspec/specs/mudblazor-setup/spec.md

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+## Purpose
+
+Define MudBlazor installation, theming, and provider configuration for the Client project.
+
+## Requirements
+
+### Requirement: MudBlazor package installed
+
+The Client project SHALL have MudBlazor 9.2.0 installed as a NuGet dependency.
+
+#### Scenario: Package reference present
+
+- **WHEN** the Client project is built
+- **THEN** MudBlazor 9.2.0 is resolved as a dependency
+
+### Requirement: MudBlazor services registered
+
+MudBlazor services SHALL be registered in the Client's DI container via `AddMudServices()`.
+
+#### Scenario: Services available
+
+- **WHEN** the application starts
+- **THEN** MudBlazor services (snackbar, dialog, etc.) are available for injection
+
+### Requirement: MudBlazor assets loaded
+
+The Client's `index.html` SHALL include MudBlazor CSS, JS, and font references.
+
+#### Scenario: Styles and scripts present
+
+- **WHEN** the application loads in the browser
+- **THEN** MudBlazor CSS (`_content/MudBlazor/MudBlazor.min.css`), JS (`_content/MudBlazor/MudBlazor.min.js`), and Material Design Icons font are loaded
+
+### Requirement: MudBlazor layout providers
+
+The app root SHALL include `MudThemeProvider`, `MudPopoverProvider`, and `MudDialogProvider` so MudBlazor components function correctly.
+
+#### Scenario: Providers present
+
+- **WHEN** any MudBlazor component is rendered
+- **THEN** it functions correctly because the required providers are in the component tree
+
+### Requirement: MudBlazor layout replaces Bootstrap
+
+The application layout SHALL use MudBlazor layout components (`MudLayout`, `MudAppBar`, `MudMainContent`) instead of the current Bootstrap navbar.
+
+#### Scenario: Layout renders with MudBlazor
+
+- **WHEN** any page is displayed
+- **THEN** the page is wrapped in a MudBlazor layout with an app bar showing the application name

openspec/specs/project/spec.md

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+## Purpose
+
+Define the project identity, core value, and non-negotiable constraints for Chat Agent WebApp.
+## Requirements
+### Requirement: Project identity
+
+The project spec SHALL contain the project name, a description paragraph, and a core value statement that communicates the project's dual purpose: working AI chat interface and Blazor learning journey.
+
+#### Scenario: Project description present
+
+- **WHEN** an AI agent or developer reads the project spec
+- **THEN** they find the project name ("Chat Agent WebApp"), a description of what the app does, and the core value statement
+
+### Requirement: Project constraints
+
+The project spec SHALL enumerate all non-negotiable constraints that govern technical decisions across the project.
+
+#### Scenario: Constraints enumerated
+
+- **WHEN** a decision is made about technology, architecture, or approach
+- **THEN** the project spec provides the authoritative list of constraints to check against:
+  - Tech stack: .NET / C# / Blazor WebAssembly
+  - LLM provider: OpenAI GPT API
+  - Storage: JSON files on local disk
+  - Architecture: WASM client + backend API (API key stays server-side)
+  - Code style: Every Blazor concept introduced MUST have inline comments explaining what it does and why
+

openspec/specs/stack/spec.md

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+## Purpose
+
+Document the technology stack decisions for Chat Agent WebApp.
+## Requirements
+### Requirement: Core technology stack
+
+The stack spec SHALL document the recommended core technologies with version, purpose, and rationale for each.
+
+#### Scenario: Core stack documented
+
+- **WHEN** a developer needs to add or update a dependency
+- **THEN** the stack spec provides the authoritative record of: .NET 9 SDK, Blazor WebAssembly Standalone, ASP.NET Core Web API, C# 13, OpenAI SDK 2.9.1, Markdig 1.1.1, MudBlazor 9.2.0, and System.Text.Json
+
+### Requirement: Supporting libraries and tools
+
+The stack spec SHALL document supporting libraries, development tools, and installation notes.
+
+#### Scenario: Supporting libraries referenced
+
+- **WHEN** a developer evaluates adding a new dependency
+- **THEN** the stack spec lists supporting libraries with guidance on when to use them (e.g., Microsoft.Extensions.AI — skip for v1)
+
+### Requirement: Alternatives and exclusions
+
+The stack spec SHALL document considered alternatives and explicitly excluded technologies with rationale.
+
+#### Scenario: Alternative considered
+
+- **WHEN** a developer proposes an alternative package or approach
+- **THEN** the stack spec provides a record of alternatives already evaluated and why the current choice was made
+
+#### Scenario: Excluded technology referenced
+
+- **WHEN** a developer considers using a technology on the exclusion list
+- **THEN** the stack spec explains why it was excluded and what to use instead
+
+### Requirement: Stack patterns
+
+The stack spec SHALL document implementation patterns that govern how stack technologies are used together (streaming, storage, markdown rendering).
+
+#### Scenario: Pattern referenced during implementation
+
+- **WHEN** a developer implements streaming, storage, or markdown rendering
+- **THEN** the stack spec provides the canonical pattern to follow
+
+### Requirement: Version compatibility matrix
+
+The stack spec SHALL maintain a compatibility matrix and list of authoritative sources for version decisions.
+
+#### Scenario: Compatibility check
+
+- **WHEN** a package version is being upgraded
+- **THEN** the stack spec provides the compatibility matrix to verify cross-package compatibility
+