v0.11.0

• JMeter engine — perfscale run --jmeter plan.jmx runs a JMeter test
  plan headless (jmeter -n -t), streams its output live, and translates the
  final console summary = line into the k6-compatible summary block
  (avg/min/max and error rate — the console summary has no percentiles).
  JMeter's exit code is the CI gate; there is no thresholds integration and
  no perfscale config mapping.
• WebSocket echo endpoint in perfscale serve — GET /ws upgrades and
  echoes every text (and binary) message back, a loopback target for
  WebSocket load tests and the new ws benchmark suite (messages/sec and
  message RTT for the native engine and k6).
• Embedding API for imports — import::resolve_value resolves the
  import: chain of an API-submitted document (no file origin), and
  ImportOptions::remote_guard lets a server veto every network target in
  the chain (SSRF protection), including HTTP redirect hops.
• HTTP plumbing is public for downstream actions — step::http now
  exposes ClientPool, client, timed_exchange, HttpOutcome,
  request_line, transport_error, and error_chain, plus
  Context::http_client_shard(), so proprietary action families (e.g.
  pro/soap) pool, time, and report HTTP exchanges identically to
  std/http@v1.
• k6-style load profiles in the native engine — stages: ramps VUs
  linearly between targets (graceful scale-down at step boundaries) and
  arrival: holds an iterations/sec rate profile with a lazily growing
  worker pool (max_vus, pre_allocated_vus). For staged/arrival runs the
  summary's vus line reports the observed concurrency
  (vus....................: <last> min=<min> max=<max>), the periodic
  [stats] line gains a trailing vus=N field (downstream parsers: the
  field appears only on staged/arrival runs; fixed-run lines are
  unchanged), summary exports report vus: null, and arrival runs surface
  a dropped_iterations metric for permits the saturated pool couldn't
  serve. Both profiles are native-engine only — --locust rejects them with
  a clear error.

Full Changelog: v0.10.0...v0.11.0