feat: default .use_skill() data argument to list()

[Copilot]

data in .use_skill() was required, forcing callers with no whisker variables to pass data = list() explicitly.

Changes

• R/use_skill.R: Add data = list() as the default for .use_skill()'s data parameter
• R/use_skill_document.R: Drop now-redundant data = list() from the .use_skill("document", ...) call
• tests/testthat/test-use_skill.R: Add test exercising .use_skill() without data

# Before: skills with no template variables required an explicit empty list
.use_skill("document", data = list(), open = FALSE)

# After: default kicks in
.use_skill("document", open = FALSE)

Original prompt

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This section details on the original issue you should resolve

<issue_title>feat: default .use_skill() data argument to list()</issue_title>
<issue_description>The data argument of .use_skill() (in R/use_skill.R and the corresponding test file) currently doesn't have a default. Add a default, list(), so that skills without whisker variables don't need to explicitly pass data = list(). Make sure the .use_skill() tests work and there's 100% coverage. Update invocation of .use_skill() (use_skill_document() in R/use_skill_document.R) to avoid passing data = list() (use the default, ie don't specify data).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes feat: default .use_skill() data argument to list() #15

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[jonthegeek]

@copilot Implement these changes.

[jonthegeek]

Fixed.