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/021a-support-logger-pii-probe.java

@@ -0,0 +1,23 @@
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
+import dev.caskeleton.adapter.outbound.support.FailOpenDependencyLogger;
+import org.slf4j.LoggerFactory;
+
+public class SupportLoggerLeakProbe {
+  public static void main(String[] args) {
+    var logger = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("probe.support.pii");
+    var appender = new ListAppender<ILoggingEvent>();
+    appender.start();
+    logger.addAppender(appender);
+    logger.setLevel(Level.DEBUG);
+    try {
+      new FailOpenDependencyLogger(logger).logFailure(
+          "google-email", "notification", "send",
+          new RuntimeException("provider rejected recipient secret@gmail.com body=secret-body-content"));
+      System.out.println(appender.list.get(0).getFormattedMessage());
+    } finally {
+      logger.detachAppender(appender);
+    }
+  }
+}