docs(git): require fenced code block output for commit messages

- enforce one code block with only message content for copy/paste
- disallow prose or labels outside the code block
- add explicit correct and wrong output examples

.ai/instructions/skills/git.instructions.md

@@ -46,7 +46,24 @@ When the user asks for a commit message:
 
 1. **Run `git diff --staged` or `git diff`** — read what actually changed
 2. **Documentation check** — scan the changed files and ask: does any `docs/` or `README.md` need updating based on these changes? If yes, flag it clearly before writing the message. Do not block the commit — just surface it.
-3. **Write the commit message only** — one short subject line, optionally a blank line and brief body if the change needs context. Output just the message text in a code block. Do NOT wrap it in a `git commit` command.
+3. **Write the commit message only** — one short subject line, optionally a blank line and brief body if the change needs context. Output must be only the message text inside one fenced code block. Do NOT wrap it in a `git commit` command.
+
+**Output format is mandatory for copy/paste:**
+- Always use one fenced code block (prefer `text` language tag)
+- Put only commit message content inside the block
+- Do not add prose before or after the block
+- Do not add labels like "Suggested message:" outside the block
+
+Correct:
+```text
+fix(scope): concise subject
+
+optional body line
+```
+
+Wrong:
+- `Suggested commit message: fix(scope): concise subject`
+- Plain text without a fenced block
 
 Format:
 ```