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/config.yaml

@@ -1,20 +1,9 @@
 schema: spec-driven
 
-# Project context (optional)
-# This is shown to AI when creating artifacts.
-# Add your tech stack, conventions, style guides, domain knowledge, etc.
-# Example:
-#   context: |
-#     Tech stack: TypeScript, React, Node.js
-#     We use conventional commits
-#     Domain: e-commerce platform
-
-# Per-artifact rules (optional)
-# Add custom rules for specific artifacts.
-# Example:
-#   rules:
-#     proposal:
-#       - Keep proposals under 500 words
-#       - Always include a "Non-goals" section
-#     tasks:
-#       - Break tasks into chunks of max 2 hours
+context: |
+  Chat Agent WebApp — personal AI chat app built with Blazor WebAssembly + OpenAI GPT API.
+  Tech stack: .NET 9, C# 13, Blazor WASM (standalone client), ASP.NET Core Web API (backend proxy).
+  Key libraries: OpenAI SDK 2.9.1, Markdig 1.1.1, MudBlazor 9.2.0, System.Text.Json.
+  Storage: JSON files on local disk. Single-user, no auth.
+  The project is also a Blazor tutorial — every concept must have inline comments explaining what and why.
+  See openspec/specs/project/ and openspec/specs/stack/ for full details.