feat(conformance): first PROVEN row — R-STATE-02 node-loss

Records the first requirement this project has ever PROVEN, in the only sense its own
definition of done accepts: a green, requirement-tagged, reproducible behaviour test,
executed against a real cluster, with the evidence committed.

  test      node-loss                      run   20260901T235117Z-e9a4b66
  req       R-STATE-02 (safety-critical)   junit passed
  sentinel  NODE_LOSS_VOLUME_AVAILABLE_OK  proof proven
  sha       57d4df8 (clean tree)           kube  v1.36.4+k3s1

What actually ran: seed a 3-replica longhorn volume, cordon the node the writer landed on,
evict only its own pod, assert the volume stays available and a reader on another node
re-attaches and reads the data back. 131s. It deliberately does NOT drain, so kubelet and
the etcd member stay up and quorum is never touched — which is what retired the old
'defer node-loss to a maintenance window' reason as unfounded rather than by fiat.

Recorded against the clean tree of the preceding commit so git_sha resolves and the
freshness check passes. The test was NOT re-run for this: the preserved run.log is the
evidence, and re-running would have proved the parser rather than preserving the run.

Serves: R-STATE-02, R-TEST-03, R-TEST-05.

conformance/runs/ledger.jsonl

@@ -0,0 +1 @@
+{"chainsaw_version": "v0.2.12", "env": "dev", "git_sha": "57d4df8c4f992732a49f3e2daddcace866778ab0", "junit_result": "passed", "kube_version": "v1.36.4+k3s1", "layer": "L3", "note": "run log OUTPUT carries every declared pass token (NODE_LOSS_VOLUME_AVAILABLE_OK) and no skip token [log scoped to this testcase; tokens read from real-output sections only]", "proof": "proven", "requirements": ["R-STATE-02"], "run_id": "20260901T235117Z-e9a4b66", "sentinel": "NODE_LOSS_VOLUME_AVAILABLE_OK", "test": "node-loss", "ts_utc": "2026-09-01T23:51:17Z"}