v0.3.1

Added

• cli: webrain install --engine lightpanda now downloads the lightpanda
  binary from the lightpanda-io/browser GitHub release (raw asset, no
  archive) into the engine cache, mirroring --engine obscura.
  find_lightpanda() also discovers the cached build, so webrain lightpanda
  just works after install. Lightpanda publishes no Windows binary — on Windows
  the install bails with the Docker fallback (lightpanda/browser:nightly)
  instead of silently installing Chrome.

Changed

• cli: webrain install --engine <unknown> now errors with a clear message
  (try chrome, obscura, or lightpanda) instead of silently installing Chrome.

Fixed

• mcp: webrain_open_session(cdp_url=…) now actually routes tools to that
  session — every browser tool accepts an optional session_id argument.
  Previously routing only worked via the Mcp-Session-Id HTTP header, so
  open_session(cdp_url=obscura) never switched navigate/batch/setcookies and
  everything kept hitting the default Chrome backend.
• mcp: a browser kill/restart no longer wedges the cached backend forever —
  dead-socket errors (os error 10054 / connection reset / stream closed) now
  drop the backend so the next call reconnects fresh.
• core: the CDP WebSocket connect retries once with a longer budget (20s)
  after the initial 5s fail-fast, tolerating obscura's slow cold-start
  handshake.