refactor(git-workflow): retrofit to the ADR-0020 context contract

Description 566 -> 249 chars, body 644 -> 398 words, Gotchas 12 -> 2. The
eight organisational hard rules move to references/hard-rules.md.

Its load trigger enumerates operations rather than rule topics: the first
draft keyed on 'commit message form', which left the atomicity and
working-state rules unreachable when a caller supplied a conventional
message. Also promotes the destructive-op confirmation ahead of the
orchestrator invocation, which it previously followed.

plugins/git/skills/git-workflow/references/README.md

@@ -9,8 +9,11 @@ source_keys:
 
 # References
 
-This directory contains provenance metadata and research sources for the `git-workflow` skill.
+This directory contains the org git rules and the provenance metadata for the `git-workflow`
+skill.
 
 ## Files
 
+- `hard-rules.md` — The org's non-negotiable git rules, loaded when a request creates, amends, or
+  rewrites a commit, pushes, or touches hooks, config, or credentials
 - `sources.md` — Extracted research sources and their contributing documents