Feat/phase c generator addons

[neo7337]

This pull request implements the final AI Agent and AI addon generation features in the backend, completes the corresponding tasks in the project plan, and updates the documentation to reflect new installation and usage options. The most significant changes are the addition of the AIAgentGenerator, AIAddonGen, and VectorStoreAddonGen implementations, as well as a major overhaul of the README.md to improve onboarding and quick start instructions.

AI Agent & Addon Generation Implementation:

• Added AIAgentGenerator in gen_ai_agent.go, which generates a complete AI agent project structure, including main.go, agent logic, tool stubs, LLM client, and optional logging/vectorstore addons, wiring all required helpers and emitting Docker support when requested.
• Implemented AIAddonGen and VectorStoreAddonGen in gen_ai_addon.go, which generate internal/ai/client.go and internal/vectorstore/store.go respectively when the relevant addons are selected, using the first selected provider/store.
• Removed placeholder implementations for these generators from registry.go, as the real implementations are now provided.

Documentation & Project Planning:

• Overhauled README.md to add clear installation instructions (including Homebrew and CLI), a quick start guide, updated supported options, and improved explanations of generated project structure and available commands.
• Marked tasks T-AI9, T-AI10, and T-AI11 as complete in tasks.md and updated the project phase summary to indicate that all AI Agent Capabilities tasks are done. Also marked the README update task as complete. [1] [2] [3]
• Marked T24 (dead config code) as complete in the infrastructure phase.