Refactor constitution.md into a template file

[dpi627]

Hi, Dev

consititution.md currently exists as a template.
Since we already have the /constitution command,
would it be more intuitive to move it to ./templates/constitution-template.md instead?

Then, when using the /constitution command, it could generate the actual constitution.md.

[SirunGameDev]

I see also the benefit that you don't delete your constitution after update with this change.

[outp1]

Another way is to just ask user before overwriting constitution with option to keep existing file.
This approach proposed there and implemented there

[gpr]

I think it would be better to have a template file, which would allow us to update spec-kit through a command like:

Execute `uvx --from git+https://github.com/github/spec-kit.git specify init --here --no-git --script sh --ai cursor`

Review the changes introduced to original templates in @.specify/templates/ and propose modification of the current constitution @.specify/memory/constitution.md and @specs/