docs(git-workflow): reduce commit context usage

[j-d-ha]

Summary

Updates the git workflow skill so commit-only requests use a compact path instead of eagerly loading shared references and unrelated workflow docs. Also tightens the commit workflow safety order so automatic exclusions are identified before staging files.

Changes

• Adds a commit-only fast path to skills/git-workflow/SKILL.md
• Updates skills/git-workflow/docs/commit.md to treat shared references as optional context for ambiguity
• Directs simple commit workflows to start from compact Git inspection before considering full diffs
• Reorders commit workflow steps to identify obvious junk, local config, generated output, and secrets before staging remaining user-modified files

Validation

• Reviewed the resulting diff with git diff --stat and git diff --name-status
• Checked git workflow skill structure against skill-creator guidance
• Verified markdown links under skills/git-workflow with a Python link check