Agent Plugins 0.19.0

A new skill investigates what cannot be re-run: a production incident, an outage, or a question
about a running system. aep:diagnosing builds a failing command first. aep:investigating
keeps the evidence and cites where every fact came from.

• New skill: aep:investigating, with ten techniques in references/techniques.md: capture
  before remediation, a sourced UTC timeline, onset from state, peer differential, negative
  claims, ship state, a hypothesis ledger, checking the check, complete reads, and the
  post-incident report. Each technique names the failure it was written from. The investigation
  is an incident-report artifact, observations are health_observation evidence, and each
  follow-up is a draft story.
• aep:diagnosing and b10x:routing send an incident that cannot be re-run to
  aep:investigating.
• No eval case covers the new skill yet; evals/README.md lists it with the uncovered ones.
• verified.json still pins aep 0.64.0 and ess 0.39.0. aep 0.65.0 and ess 0.42.0 are not yet
  re-verified: agentplugins-check tools reports aep plan artifact divergences, spelled in
  aep:planning, as not a command of aep 0.65.0.