docs: classify test planning documents

tests/LAYOUT_INVENTORY.md

@@ -10,6 +10,23 @@
 - **Implemented by:** #3842
 - **Status:** completed historical snapshot
 
+- **Durable testing policy:** [`TESTING_STANDARD.md`](./TESTING_STANDARD.md)
+- **Current testing mechanics:** [`README.md`](./README.md)
+
+## Disposition
+
+This document is retained as a non-canonical historical record of the completed
+CLI test relocation.
+
+Reusable testing rules are maintained in `TESTING_STANDARD.md`; current helper,
+taxonomy-runner, and execution mechanics are maintained in `README.md`, the test
+suite, and its supporting code.
+
+Counts, residual-file observations, and path listings in this document are
+snapshot evidence only. They must not be maintained as durable repository truth.
+
+Any additional test relocation requires a separately approved issue or work item.
+
 ## Purpose
 
 This document preserves the reasoning, scope, and validation contract for the

tests/OVERSIZED_TEST_SPLIT_PLAN.md

@@ -2,6 +2,10 @@
 
 > [!NOTE]
 > This is generated planning material based on the current test tree.
+>
+> It is non-canonical and disposable. Durable testing policy belongs in
+> `tests/TESTING_STANDARD.md`; active split selection and prioritization
+> belong in approved issues or the project tracker.
 > It does not define runtime behaviour or approve any test-file split.
 
 ## Purpose

tests/tools/build_oversized_test_split_plan.py

@@ -443,6 +443,10 @@ def write_report(metrics: list[FileMetric], node_count_total: int) -> None:
         "",
         "> [!NOTE]",
         "> This is generated planning material based on the current test tree.",
+        ">",
+        "> It is non-canonical and disposable. Durable testing policy belongs in",
+        "> `tests/TESTING_STANDARD.md`; active split selection and prioritization",
+        "> belong in approved issues or the project tracker.",
         "> It does not define runtime behaviour or approve any test-file split.",
         "",
         "## Purpose",