Save template for constitution along with the other templates.

[rkaramc]

Save template for constitution along with the other templates, instead of overwriting the instantiated file.

...
.specify/memory/constitution.md was overwritten with the default template, but not a big deal - easy to not commit that.

Originally posted by @kierankelleher in #377

I understand current recommendation is to revert changes to the file. However, the changes to the template will also be lost making it difficult to update the current constitution to match.

If the template is in a different location, it would make it possible for an agent to compare and update as needed.