Add a cherry-pick skill for copilot

[alsepkow]

Adds a cherry-pick skill at .github/skills/cherry-pick/SKILL.md.

Rather than putting the convention in .github/copilot-instructions.md (which is injected into every prompt), a skill is auto-discovered from the repo and only loaded on demand when a cherry-pick is actually being done. The skill captures:

• Cherry-pick commits using git cherry-pick -x so the source SHA is recorded in git's standard format.
• Keep the cherry-pick commit message as git generates it by default.
• Prefix the PR title with [Cherry-Pick].

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[damyanp]

This seems like a lot of text to add to every single prompt. I think this might be something we'd want to do as a skill. But really I think we don't need much more than "Use git cherry-pick -x for cherry picks". I actually think we shouldn't diverge too much from the commit message that git generates by default for this. I think instructions about how to create topic branches and stuff don't need to be explicit here.

[bob80905]

LGTM

[alsepkow]

This seems like a lot of text to add to every single prompt. I think this might be something we'd want to do as a skill. But really I think we don't need much more than "Use git cherry-pick -x for cherry picks". I actually think we shouldn't diverge too much from the commit message that git generates by default for this. I think instructions about how to create topic branches and stuff don't need to be explicit here.

Swapped to a skill. Confirmed locally that it loads automatically on copilot startup