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/agents/sources.md

@@ -0,0 +1,55 @@
+---
+name: git-agents-sources
+description: Provenance record for the git plugin's agents, not an invokable agent. Do not invoke.
+tools: none
+---
+
+# Sources
+
+## context7-git-htmldocs
+
+- **URL:** context7:/git/htmldocs
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** Official Git HTML documentation from the git/htmldocs repository — covers all commands, concepts, and internals.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`
+
+## git-scm-docs
+
+- **URL:** https://git-scm.com/docs/git-config
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** Official git-scm.com reference pages — git-config manual and CLI reference.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`
+
+## git-scm-worktree-docs
+
+- **URL:** https://git-scm.com/docs/git-worktree
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** Official git-scm.com reference for git-worktree — subcommands, flags, ref-sharing rules.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`
+
+## git-scm-submodule-docs
+
+- **URL:** https://git-scm.com/docs/git-submodule
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** Official git-scm.com reference for git-submodule — subcommands, flags, configuration keys.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`
+
+## git-scm-remote-docs
+
+- **URL:** https://git-scm.com/docs/git-remote
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** Official git-scm.com reference for git-remote — add, remove, rename, set-url, prune.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`
+
+## conventional-commits-spec
+
+- **URL:** https://www.conventionalcommits.org/en/v1.0.0/
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md
+- **Description:** The Conventional Commits v1.0.0 specification — format rules, breaking change conventions, footer token format.
+- **Contributing files:** agents/git-orchestrate.md, agents/git-orchestrate.agent.md
+- **Status:** `extracted`