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-commits/references/sources.md

@@ -0,0 +1,40 @@
+---
+topic: commits
+source_keys:
+  - conventional-commits-spec
+  - commitlint-config-conventional
+  - org-commit-conventions
+  - context7-git-htmldocs
+---
+
+# Research Sources for git:commits Skill
+
+Sources extracted from the git plugin research phase. Only sources that directly informed this skill are listed; sibling skills (git:branches, git:history, git:remotes, etc.) have their own sources.md.
+
+## conventional-commits-spec
+
+- **Description:** Conventional Commits Specification (v1.0.0) — message format, types, breaking changes, footer rules
+- **Research doc:** plugins/git/docs/research/docs/git/commits.md § "Conventional Commits Specification (v1.0.0)"
+- **Contributing files:** SKILL.md, references/conventional-commits-spec.md
+- **Status:** extracted
+
+## commitlint-config-conventional
+
+- **Description:** commitlint config-conventional preset — validation constraints (max 100 chars header, no trailing periods, lowercase type, 11-type set enforcement)
+- **Research doc:** plugins/git/docs/research/docs/git/commits.md § "commitlint Constraints (`config-conventional`)"
+- **Contributing files:** SKILL.md, references/conventional-commits-spec.md
+- **Status:** extracted
+
+## org-commit-conventions
+
+- **Description:** Organization commit message body template and git conventions (atomic commits, no `--no-verify`, no force-push main/master, `rtk git` wrapper) — content fully embedded in this skill; the org's `core/instructions/git.md` and `core/instructions/commits.md` are provenance only and are not a live dependency
+- **Research doc:** core/instructions/commits.md, core/instructions/git.md (org convention, not part of the plugin's research corpus)
+- **Contributing files:** SKILL.md, references/commit-template.md
+- **Status:** extracted
+
+## context7-git-htmldocs
+
+- **Description:** Official Git HTML documentation — `git commit --squash`/`--fixup` and `git rebase --autosquash` flag semantics
+- **Research doc:** plugins/git/docs/research/docs/git/cli-reference.md
+- **Contributing files:** SKILL.md
+- **Status:** extracted