docs(keycloak-session-store): import the session-storage lab as a new project

The keycloak project ended with four open questions that design could not
settle. A two-VM lab was built to answer them by measurement, and this is
that material: 26 experiments, 125 raw command outputs, 22 browser captures.

Follows the import procedure in README.md.

  source/     the originating repository verbatim — 78 documents, 28 SVGs,
              8 manifests, plus .source-revision recording the commit
  final/      the SSOT
    document.md   729 lines written from the 29 experiment documents, not
                  concatenated: what was predicted, what was measured, and
                  where the measurement itself was wrong
    evidence/raw    125 outputs, flattened to <experiment>__<file> because
                    the originals collided (01-baseline.txt appeared three
                    times) and the audit only globs the top level
    evidence/meta   one per raw file; command and exitCode are null and the
                    README says why rather than inventing them
    evidence/browser  22 captures
    assets/       three diagrams through techviz
    .techviz/     their VizSpecs

A separate project rather than an addition to keycloak: the B-layer answers
that project's four questions, but the A, C and D layers are about cluster
failure, SSO and operations, and one document.md should hold one subject.
The four question records there can point here through 관계.

Recorded rather than papered over: only three of the 28 diagrams were
remade. The repository forbids hand-drawn SVG and forbids titles inside the
canvas; all 28 originals carry both, so converting them is redrawing, not
reformatting. They stay in source/ and the gap is written into the document.

verify-pipeline.py passes. audit-records.py reports no issues.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/clean-architecture-backend-template/final/evidence/raw/a11-f004-number.txt

@@ -0,0 +1,41 @@
+# 검사가 선언하는 범위
+ * <p>The check is structural and conservative: records, enums, strings, boxed primitives and
+ * immutable collection views replay; anything else is treated as one-shot, so the retry engine
+ * refuses rather than gambling. A caller who knows better can freeze the value itself — serialize
+ * it to a {@code byte[]} body — which states the guarantee instead of asserting it.
+ */
+
+# 첫 분기
+  private static boolean deeplyImmutable(Object candidate) {
+    if (candidate == null) {
+      return true;
+    }
+    if (candidate instanceof String
+        || candidate instanceof Number
+        || candidate instanceof Boolean
+        || candidate instanceof Character
+        || candidate instanceof Enum<?>
+        || candidate instanceof java.util.UUID
+        || candidate instanceof java.time.temporal.Temporal) {
+      return true;
+    }
+
+# 이 검사가 존재하는 이유 (test 클래스 javadoc)
+/**
+ * Replayability is a property of the value, not a promise in a javadoc.
+ *
+ * <p>Every {@code ObjectBody} used to report {@code REPLAYABLE}. A caller who reused a builder or
+ * kept a reference to a list therefore got a retry that re-encoded the value <em>as it was at retry
+ * time</em> — different bytes, same idempotency key, which is precisely what a replay must never
+ * be.
+ */
+
+# 그 이유를 고정하는 test 넷
+  28:  @DisplayName("a record of immutable components replays")
+  29:  void anImmutableRecordReplays() {
+  41:  @DisplayName("a value the caller can still mutate does not replay")
+  42:  void aMutableValueIsOneShot() {
+  51:  @DisplayName("a record wrapping a mutable component does not replay")
+  52:  void aRecordWrappingMutableStateIsOneShot() {
+  66:  @DisplayName("an uninspectable value is one-shot")
+  67:  void anArbitraryBeanIsOneShot() {