Support using templates in `skip: run` fields

[neefrehman]

Description

I've noticed that templated scripts cannot be run when passed to the skip field.

templates:
  skip_slow_hooks: '[ "$CLAUDECODE" != "1" ];'

pre-commit:
  parallel: true
  jobs:
    - name: "Typecheck"                                                                                                      
      skip:                                                                                                                  
        - run: '{skip_slow_hooks}' # doesn't work                                                                             
      run: 'uv run npx pyright --threads 4 {staged_files}'

templates:
  skip_slow_hooks: '[ "$CLAUDECODE" != "1" ]; then exit 0; fi &&'

pre-commit:
  parallel: true
  jobs:
    - name: "Typecheck"                                                                                                                                                                             
      run: '{skip_slow_hooks} uv run npx pyright --threads 4 {staged_files}' # works

What problem it is solving?

As can be seen, I'm trying to implement an easily overridable config where Claude code commit will trigger more extensive hooks, and also any user who wants to opt in can do so via their local config file. While skip is more verbose, I think it is easier to reason about than manually gating commands via early exits. skip also allows you to skip a whole group at once.