feat(model+spec): .cph-version 契约文件 + CphVersionMismatch 诊断(ADR-0016);bump 0.0.2

教研工程文件根放 .cph-version(内容=面向的 cph 版本)。cph 加载时比对自身版本
(CARGO_PKG_VERSION),不相容报 CphVersionMismatch error 并拒绝。当前判定为版本完全
相等(MVP);判定逻辑孤立在 versions_compatible 单谓词,后续可放宽为 semver 区间而
不动诊断分类/spec/CLI。

spec(7 类诊断,原 6 类):
- Diagnostic.lean: DiagKind 增 cphVersionMismatch(error 级),分类注释 6→7
- Pipeline.lean: load 阶段含 .cph-version 兼容性判定
- Courseware.lean: ADR 区间 →0016

实现:
- cph-diag: DiagCode::CphVersionMismatch("E-CPH-VERSION")
- cph-model: load() 解析 manifest 成功后 check_cph_version;versions_compatible
  谓词(完全相等);CPH_VERSION const。missing .cph-version 暂跳过(迁移期 OPEN);
  空文件报 error
- examples/TH-141、valid/mini fixture、KenKen 课各加 .cph-version=0.0.2

测试:cph-model 4 个版本门测试;全 workspace 53 passed;lake 25 jobs 绿。
负向验证:9.9.9 .cph-version → E-CPH-VERSION error + check 拒绝(exit 1)。

bump: workspace.package 0.0.1→0.0.2;cph --version 报 cph 0.0.2;README 同步
(含版本契约说明)。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/cph-model/tests/load.rs

@@ -272,3 +272,90 @@ fn malformed_target_config_is_non_fatal_with_schema_violations() {
         "a diagnostic should name the bad step type, got: {diags:?}"
     );
 }
+
+// --- `.cph-version` compatibility gate (ADR-0016) ------------------------------
+
+/// The cph version the running CLI was built with — what `.cph-version` must
+/// match exactly (ADR-0016's MVP rule).
+const CPH_VERSION: &str = env!("CARGO_PKG_VERSION");
+
+/// Write a one-part lesson into a temp dir, optionally with a `.cph-version`
+/// file. Returns the temp dir so the caller runs `load`.
+fn tmp_lesson_with_version(version: Option<&str>) -> PathBuf {
+    let mut p = std::env::temp_dir();
+    let nanos = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap()
+        .as_nanos();
+    p.push(format!("cph-version-test-{nanos}"));
+    std::fs::create_dir_all(&p).unwrap();
+    std::fs::write(
+        p.join("manifest.toml"),
+        "[project]\nid = \"v\"\nname = \"v\"\n[info]\ntitle = \"v\"\n[[parts]]\nkind = \"segment\"\npath = \"segments/a\"\n",
+    )
+    .unwrap();
+    let seg = p.join("segments").join("a");
+    std::fs::create_dir_all(&seg).unwrap();
+    std::fs::write(seg.join("element.toml"), "kind = \"segment\"\n").unwrap();
+    std::fs::write(seg.join("textbook.typ"), "t.\n").unwrap();
+    if let Some(v) = version {
+        std::fs::write(p.join(".cph-version"), v).unwrap();
+    }
+    p
+}
+
+#[test]
+fn cph_version_matching_is_not_a_diagnostic() {
+    let tmp = tmp_lesson_with_version(Some(CPH_VERSION));
+    let (_lesson, diags) = load(&tmp);
+    let _ = std::fs::remove_dir_all(&tmp);
+    assert!(
+        diags.iter().all(|d| d.code != DiagCode::CphVersionMismatch),
+        "a matching .cph-version must not warn, got {diags:?}"
+    );
+}
+
+#[test]
+fn cph_version_mismatch_is_an_error_diagnostic() {
+    let tmp = tmp_lesson_with_version(Some("99.99.99"));
+    let (lesson, diags) = load(&tmp);
+    let _ = std::fs::remove_dir_all(&tmp);
+    // The lesson still loads (so other defects could surface), but the
+    // mismatch is an error diagnostic — which alone makes it illegal.
+    assert!(lesson.is_some(), "a mismatch should not halt loading");
+    let mm: Vec<_> = diags
+        .iter()
+        .filter(|d| d.code == DiagCode::CphVersionMismatch)
+        .collect();
+    assert_eq!(mm.len(), 1, "expected one CphVersionMismatch, got {diags:?}");
+    assert!(
+        mm[0].message.contains("99.99.99") && mm[0].message.contains(CPH_VERSION),
+        "diagnostic should name both versions, got: {}",
+        mm[0].message
+    );
+}
+
+#[test]
+fn cph_version_missing_is_skipped() {
+    // No `.cph-version` file at all → skipped (ADR-0016 migration period; OPEN).
+    let tmp = tmp_lesson_with_version(None);
+    let (_lesson, diags) = load(&tmp);
+    let _ = std::fs::remove_dir_all(&tmp);
+    assert!(
+        diags.iter().all(|d| d.code != DiagCode::CphVersionMismatch),
+        "a missing .cph-version must be skipped, got {diags:?}"
+    );
+}
+
+#[test]
+fn cph_version_empty_is_an_error() {
+    let tmp = tmp_lesson_with_version(Some("   \n"));
+    let (_lesson, diags) = load(&tmp);
+    let _ = std::fs::remove_dir_all(&tmp);
+    assert!(
+        diags
+            .iter()
+            .any(|d| d.code == DiagCode::CphVersionMismatch && d.message.contains("empty")),
+        "an empty .cph-version should be an error, got {diags:?}"
+    );
+}