Constitution template should be in .specify/templates/ to prevent overwrites during reinitialization

[LoveJazzTZ]

Problem

The constitution.md template currently resides in .specify/memory/constitution.md by default. This causes user-customized constitutions to be overwritten when spec kit is reinitialized (e.g., when setting up for a different AI agent in the same project).

Steps to Reproduce

1. Initialize spec kit in a project: /speckit.init
2. Customize .specify/memory/constitution.md with project-specific principles
3. Run spec kit initialization again (e.g., for a different agent/configuration)
4. Result: The customized constitution.md is overwritten with the template version

Expected Behavior

The customized constitution.md should be preserved across reinitialization. Only the template files in .specify/templates/ should be updated/overwritten.

Proposed Solution

1. Move the default constitution template from .specify/memory/constitution.md to .specify/templates/constitution.md
2. On first initialization (when memory/constitution.md doesn't exist), copy the template from templates/ to memory/
3. On subsequent initializations, check if memory/constitution.md exists:
   • If it exists, skip copying (preserve user's version)
   • If it doesn't exist, copy from template

Benefits

• Prevents accidental loss of customized constitutions
• Allows the same .specify/ structure to work with multiple AI agents without conflicts
• Aligns with the principle that .specify/memory/ contains project-specific artifacts, while .specify/templates/ contains reusable scaffolds

Workaround (Current)

Users must manually restore their constitution after reinitialization:

git restore .specify/memory/constitution.md