docs: describe the fix field and the concrete suggestions (#32)

> **Held until the next commit-check release.** The `fix` field lives on
commit-check `main` (commit-check/commit-check#564) and is not in the
released 2.16.0 that this site pins. Merge this together with the
release's version bump.

## What

Follows commit-check/commit-check#564, which makes a failed check name
its correction when the fix is unambiguous and carries it in a new `fix`
field of the JSON output.

- **Command-line recipes → Reading the JSON**: explains `fix`, shows a
failed CC001 check with `suggest` and `fix` populated, and states when
`fix` stays empty (a subject with no type, a length limit, a
non-imperative verb).
- **Rules reference**: next to the generic sample output, a sample where
the suggestion names the correction (`Suggest: Use "fix: add x"`), taken
verbatim from the tool.

The MCP guide is unchanged: commit-check-mcp 0.1.9 does not pass `fix`
through yet. That guide gets its paragraph when the server does.

## Notes

- Sample outputs are the tool's real output and pass the docs-sync tests
(9 passed).
- No changelog entry: the changelog is written per release.
- Netlify deploy preview builds.

Author: shenxianpeng

docs/example.md

@@ -276,3 +276,30 @@ CC001
 Each failed check carries the rule ID, the offending value, the suggestion and
 a link to its documentation — the same information the text output prints, in a
 form other tools can consume.
+
+When the correction is mechanical — a type written `Fix` where `fix` is
+allowed, a letter out of place, a missing colon, a `WIP:` marker, a missing
+`Signed-off-by` trailer, a branch typed `Feature/x` — the check also carries
+the corrected value in `fix`, and `suggest` names it:
+
+```console
+$ echo "Fix: add streaming support" | commit-check -m --format json | jq '.checks[0]'
+```
+
+```json
+{
+  "rule_id": "CC001",
+  "check": "message",
+  "status": "fail",
+  "value": "Fix: add streaming support",
+  "error": "The commit message should follow Conventional Commits. See https://www.conventionalcommits.org",
+  "suggest": "Use \"fix: add streaming support\"",
+  "fix": "fix: add streaming support",
+  "docs_url": "https://commit-check.com/rules/#cc001"
+}
+```
+
+`fix` is empty whenever the correction takes a judgment — a subject with no
+type at all, one over the length limit, a verb that is not imperative — and
+`suggest` then keeps the rule's general advice. A tool can apply a non-empty
+`fix` as it stands; a person only ever needs `suggest`.

docs/rules.md

@@ -20,6 +20,17 @@ explanation, suggestion, and documentation link:
 [FAIL] CC003 subject_imperative: docs: revamped the profile
 ```
 
+When the correction is mechanical, the suggestion names it instead of
+repeating the rule — and `--format json` carries the corrected value in a
+`fix` field (see [Reading the JSON](example.md#reading-the-json)):
+
+```text
+CC001 message check failed ==> Fix: add x
+The commit message should follow Conventional Commits. See https://www.conventionalcommits.org
+Suggest: Use "fix: add x"
+Docs: https://commit-check.com/rules/#cc001
+```
+
 ## How to read this page
 
 Rule IDs are grouped by what they inspect: