[Doc] Document precheck-pr skill in PR template and contributing guide

Add precheck-pr reference to PULL_REQUEST_TEMPLATE.md BEFORE SUBMITTING
section, and add a new "Pre-Check with Claude Code" subsection to the
contributing guide.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: hsliu <liuhongsheng4@huawei.com>

docs/contributing/README.md

@@ -116,6 +116,20 @@ Only specific types of PRs will be reviewed. The PR title is prefixed appropriat
 !!! note
     If the PR spans more than one category, please include all relevant prefixes.
 
+### Pre-Check with Claude Code
+
+Before submitting a PR, run the `precheck-pr` Claude Code skill for a self-review against project conventions:
+
+```
+/precheck-pr
+```
+
+The skill offers two modes:
+- **Quick (~3 min):** catches showstoppers — PR title format, missing benchmark claims, rebase status
+- **Full (~10 min):** thorough maintainer-grade review — dead code scan, copy-paste detection, import hygiene
+
+The precheck covers five PR types: Bug Fix, Performance, New Model, Diffusion Model, and General. Each type has a tailored checklist that validates evidence quality (repro steps, A/B benchmarks, registry entries, etc.). See the skill in `.claude/skills/precheck-pr/` for the full checklist.
+
 ### Local Test
 Please run the L1 and L2 test cases locally first and attach the results before contacting us to add the "ready" label. Please refer to the [test instructions](./ci/test_guide.md) for running the test cases.