feat(git-plugin): add complete git workflow automation suite

## Why
The git plugin only covered a partial slice of common git workflows.
This adds the remaining skill set (branches, commits, history, remotes,
submodules, workflow, worktrees) plus a git-orchestrate agent so the
plugin can handle end-to-end git automation instead of a handful of
commands.

## Implementation Notes
Each new skill was validated against its research docs and org
conventions after initial authoring, which surfaced hallucinated
version pins, factual errors, and completeness gaps that were
corrected in the same pass rather than left for follow-up.

## Impact
Bumps the git plugin to 1.3.0.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

plugins/git/skills/git-remotes/README.md

@@ -0,0 +1,24 @@
+# git-remotes
+
+Manage git remote repositories — add/remove/configure remotes, push/pull with safety checks, fetch with pruning, and multi-remote workflows.
+
+## What it does
+
+This skill handles remote operations within the git workflow suite. It manages remote configuration (add, remove, rename), fetch operations with pruning, push operations with force-push safety (`--force-with-lease --force-if-includes`), and pull strategies (fast-forward, rebase, merge). It returns structured results suitable for agent composition.
+
+## Usage
+
+```
+/git-remotes
+```
+
+Describe your remote operation: add a remote, push, pull, fetch, or configure tracking. The skill will handle the operation with appropriate safety checks and return results.
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `SKILL.md` | Skill instructions for agents |
+| `references/README.md` | Describes the references directory contents |
+| `references/remotes.md` | Full `set-url` variants, shallow-clone/fetch options, force-push mitigation detail, and pull config precedence |
+| `references/sources.md` | Research sources and provenance |