v10.2.5 - Enhance console app with Spectre.Console menu, dynamic example discovery, and ChatClientLLMProvider docs

[techbuzzz]

This PR modernizes the Delibera.ConsoleApp with a Spectre.Console-powered
interactive experience and documents the Microsoft.Extensions.AI integration.

Changes

Console app (Spectre.Console)

• Add Spectre.Console 0.57.2 NuGet reference
• Replace the hardcoded ASCII banner with FigletText + centered Text + Rule
• Replace the manual args.Contains("--xyz") if-chain with a dynamic
  ExampleRegistry that discovers every example by reflection
• Add an interactive SelectionPrompt menu (grouped by category) shown when
  no CLI flag is given and stdin is a TTY
• Add --list to print the example catalog as a Spectre table
• Preserve all documented CLI flags as stable ids / aliases (--di, --msai,
  --chatclient, --pgvector, --multiprovider, --separate-files, --rag,
  --operator, --operator-mcp, --autochunking, --cancellation,
  --resilience, --compression, --quick)
• Migrate the default debate path to Spectre markup (Markup.Escape for model
  output) and Rule separators; keep WriteLogEntry/WriteErrorEntry on
  Console for thread-safe streaming
• Replace the ad-hoc fatal-error block with a Spectre Panel (rounded border)
• Add a --chatclient example (ChatClientLLMProviderExample) demonstrating
  ChatClientLLMProvider + MicrosoftAIExtensions (chat, streaming,
  embeddings, reverse bridge) using local Ollama, with the OpenAI variant in
  comments

Documentation

• Add docs/ChatClientLLMProvider.md — full provider list (OpenAI, Azure
  OpenAI, Microsoft Foundry, Anthropic, Ollama, GitHub Copilot, LM Studio /
  vLLM / LocalAI, ONNX, custom), interop bridge table, OpenAI / Azure /
  Ollama / OpenAI-compatible / streaming / embeddings / DI examples,
  capabilities & limitations
• Update src/README.md:
  • New "🔌 Pluggable LLM Backends (Microsoft.Extensions.AI)" section with a
    providers table, interop table, and link to the new doc
  • Add --chatclient and --msai to the ConsoleApp examples block
  • Add Microsoft.Extensions.AI to the NuGet dependencies table
  • Add the new section to the Table of Contents

Related Issues

N/A

Type of Change

• ✨ New feature (non-breaking change that adds functionality)
• 📚 Documentation update
• 🧹 Refactor / chore

Checklist

• My code follows the project's coding standards
• The solution builds with 0 errors and 0 warnings (dotnet build)
• I have added/updated XML documentation for public APIs
  (ExampleRegistry, ExampleEntry)
• I have updated relevant documentation (README.md,
  docs/ChatClientLLMProvider.md)
• I have tested my changes (--list resolves all 14 examples; documented
  flags resolve via the alias system)

Additional Notes

• Adding a new example file under Examples/ requires zero changes to
  Program.cs or ExampleRegistry — it is auto-discovered. Add curated
  metadata (title/category/aliases) to ExampleRegistry.Metadata only when
  you want a friendly id or aliases beyond the auto-derived kebab name.
• The default config-driven debate path is fully preserved; only the output
  rendering changed (Spectre markup instead of Console.WriteLine).
• WriteLogEntry/WriteErrorEntry intentionally stay on Console (not
  AnsiConsole.MarkupLine) because they fire from the executor's background
  threads and may contain arbitrary model output with Spectre markup chars.