docs validator: handle plan link fragments and avoid duplicate link errors

tests/test_validate_ouroboros_docs.py

@@ -19,8 +19,8 @@ def test_validate_plan_source_link_accepts_canonical_source_path() -> None:
     errors: list[str] = []
     path = Path("docs/ouroboros/README.md").resolve()
 
-    module.validate_plan_source_link(path, "./source/ouroboros_plan_v2.txt", errors)
-    module.validate_plan_source_link(path, "./source/ouroboros_plan_v3.txt", errors)
+    assert module.validate_plan_source_link(path, "./source/ouroboros_plan_v2.txt", errors) is False
+    assert module.validate_plan_source_link(path, "./source/ouroboros_plan_v3.txt", errors) is False
 
     assert errors == []
 
@@ -30,12 +30,13 @@ def test_validate_plan_source_link_rejects_root_relative_path() -> None:
     errors: list[str] = []
     path = Path("docs/ouroboros/README.md").resolve()
 
-    module.validate_plan_source_link(
+    handled = module.validate_plan_source_link(
         path,
         "/home/agentson/repos/The-Ouroboros/ouroboros_plan_v2.txt",
         errors,
     )
 
+    assert handled is True
     assert errors
     assert "invalid plan link path" in errors[0]
     assert "use ./source/ouroboros_plan_v2.txt" in errors[0]
@@ -46,8 +47,35 @@ def test_validate_plan_source_link_rejects_repo_root_relative_path() -> None:
     errors: list[str] = []
     path = Path("docs/ouroboros/README.md").resolve()
 
-    module.validate_plan_source_link(path, "../../ouroboros_plan_v2.txt", errors)
+    handled = module.validate_plan_source_link(path, "../../ouroboros_plan_v2.txt", errors)
 
+    assert handled is True
     assert errors
     assert "invalid plan link path" in errors[0]
     assert "must resolve to docs/ouroboros/source/ouroboros_plan_v2.txt" in errors[0]
+
+
+def test_validate_plan_source_link_accepts_fragment_suffix() -> None:
+    module = _load_module()
+    errors: list[str] = []
+    path = Path("docs/ouroboros/README.md").resolve()
+
+    handled = module.validate_plan_source_link(path, "./source/ouroboros_plan_v2.txt#sec", errors)
+
+    assert handled is False
+    assert errors == []
+
+
+def test_validate_links_avoids_duplicate_error_for_invalid_plan_link(tmp_path) -> None:
+    module = _load_module()
+    errors: list[str] = []
+    doc = tmp_path / "doc.md"
+    doc.write_text(
+        "[v2](/home/agentson/repos/The-Ouroboros/ouroboros_plan_v2.txt)\n",
+        encoding="utf-8",
+    )
+
+    module.validate_links(doc, doc.read_text(encoding="utf-8"), errors)
+
+    assert len(errors) == 1
+    assert "invalid plan link path" in errors[0]