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

Description 724 -> 214 chars, body 1102 -> 343 words, Gotchas 12 -> 3.
Create, rewrite, and cherry-pick flows move to self-contained references/
files behind a dispatch table.

The audit caught that moving the secret scan into the create flow left the
amend/squash path with no check in its loaded context; it is now a gate
common to every flow. Also re-homes the interactive-rebase reflog warning
git-history dropped, since this skill owns rebase.

plugins/git/skills/git-commits/references/conventional-commits-spec.md

@@ -10,7 +10,7 @@ Conventional Commits is a lightweight convention on top of commit messages that
 
 ## Message Format
 
-```
+```text
 <type>[optional scope]: <description>
 
 [optional body]
@@ -58,20 +58,20 @@ A `BREAKING CHANGE` footer or `!` on **any** type always triggers a MAJOR bump.
 Two equivalent notations:
 
 **`!` in header** (preferred — visible in `git log --oneline`):
-```
+```text
 feat!: drop support for Node 6
 feat(api)!: remove deprecated endpoint
 ```
 
 **`BREAKING CHANGE` footer** (machine-readable body):
-```
+```text
 feat: allow config to extend other configs
 
 BREAKING CHANGE: `extends` key now used for extending config files
 ```
 
 **Both together** (most explicit):
-```
+```text
 feat!: drop support for Node 6
 
 BREAKING CHANGE: use JavaScript features not available in Node 6.
@@ -85,7 +85,7 @@ Rules:
 
 ## Footer Token Rules
 
-```
+```text
 <token>: <value>
 <token> #<value>    # for issue references
 ```
@@ -96,7 +96,7 @@ Rules:
 - Blank line required before the footer block.
 
 Valid footer examples:
-```
+```text
 Reviewed-by: Z
 Refs: #123
 Co-authored-by: Alice <alice@example.com>
@@ -106,29 +106,29 @@ BREAKING CHANGE: the `--format` flag now requires a value
 ## Examples
 
 Minimal — no body, no footer:
-```
+```text
 docs: correct spelling of CHANGELOG
 ```
 
 With scope:
-```
+```text
 feat(lang): add Polish language
 ```
 
 Breaking change via `!`:
-```
+```text
 feat!: send an email to the customer when a product is shipped
 ```
 
 Breaking change via footer:
-```
+```text
 feat: allow provided config object to extend other configs
 
 BREAKING CHANGE: `extends` key in config file is now used for extending other config files
 ```
 
 Multi-paragraph body with multiple footers:
-```
+```text
 fix: prevent racing of requests
 
 Introduce a request id and a reference to latest request. Dismiss
@@ -142,7 +142,7 @@ Refs: #123
 ```
 
 Revert:
-```
+```text
 revert: let us never again speak of the noodle incident
 
 Refs: 676104e, a215868