feat: implementation of architectural impact analyzer utility

[UmmeHabiba1312]

Overview

This PR introduces a specialized Architectural Impact Analyzer to the Spec-Kit ecosystem. It enables developers to preview risks and complexity of a proposed change across all specifications before moving to the implementation phase.

Key Features

• Context-Aware Analysis: Dynamically scans .specify/memory (or default presets) to provide the AI with a holistic architectural view.
• Zero-Config Integration: Automatically inherits existing environment variables (AI_API_KEY, ANTHROPIC_API_KEY, AI_MODEL_ID) from the user's current CLI session no extra setup required.
• Provider Agnostic: Built on standard patterns to support OpenAI, Anthropic, and custom base URLs/models.
• Structured Reports: Generates professional CLI-native reports including complexity scores, estimated effort, and specific architectural risks.

Implementation Details

• scripts/impact_analyzer.py: The core analysis engine with smart path resolution and environment detection.
• templates/commands/preview.md: Native template that triggers the analyzer as a standard Spec-Kit command.
• Registry Updates: Fully integrated into specify_cli registry and Claude Code hints for a seamless user experience.

Fixes #2176

[UmmeHabiba1312]

Hi @mnriem,
I've just pushed a significant refactor to ensure this feature feels native to Spec-Kit. The analyzer now dynamically resolves paths (handling both project-specific .specify folders and default presets) and automatically inherits the existing AI environment context. This eliminates the need for redundant API key configurations and ensures a seamless UX. Ready for a deep dive review!