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/keycloak-session-store/source/deploy/lab/cloud-init/kc-lab.yaml.example

@@ -0,0 +1,37 @@
+#cloud-config
+# Template for both lab guests. scripts/rebuild-seed.sh substitutes __NODE__
+# and bakes this into a CIDATA seed image.
+#
+# Copy to kc-lab.yaml and fill the two placeholders. The real file is ignored by
+# git because plain_text_passwd is a credential, however disposable.
+#
+# Indentation is spaces only. YAML forbids tabs, and cloud-init fails silently
+# on a parse error: the guest boots as "localhost" with no user and no way in.
+hostname: kc-lab-__NODE__
+fqdn: kc-lab-__NODE__
+manage_etc_hosts: true
+
+users:
+  - name: donghyeon
+    groups: [sudo]
+    shell: /bin/bash
+    # NOPASSWD is required: the k3s installer and the fault-injection scripts
+    # run non-interactively and would block on a password prompt.
+    sudo: ['ALL=(ALL) NOPASSWD:ALL']
+    # Console-only escape hatch. Without it, a cloud-init failure leaves a guest
+    # that cannot be logged into at all, so its own failure log is unreadable.
+    # ssh_pwauth stays false, so this never widens SSH exposure.
+    lock_passwd: false
+    plain_text_passwd: CHANGE_ME
+    ssh_authorized_keys:
+      # Lab host key: needed because automation runs from the lab host, where
+      # agent forwarding is not available.
+      - CHANGE_ME_LAB_HOST_PUBLIC_KEY
+      # Workstation key: lets ProxyJump reach the guest directly.
+      - CHANGE_ME_WORKSTATION_PUBLIC_KEY
+
+ssh_pwauth: false
+package_update: true
+packages:
+  - curl
+  - nftables