v1.5.2 — runner and nested-action fixes

Runner and nested-action fixes: hooks that halt, kwargs that survive hooks,
nested actions that neither wipe parent ivars nor commit failed writes.
Requires field_struct 0.11.0 or later.

Changed

• Requires field_struct >= 0.11. It is the release whose numeric and input
  fixes this one is tested against; CI now pins it by tag.
• CI runs Ruby 3.2, 3.3, 3.4 and 4.0 (was 3.3.6 only), plus the docs guard,
  behind one aggregate ci check that main requires.
• The packaged gem leaves out contributor-only files (.claude/,
  CLAUDE.md, docs/origin/, Rakefile/Steepfile/lint config). It still ships
  lib/, sig/, the user docs, AGENTS.md and the Claude skill.

Fixed

• A failed transactional action inside an outer transaction no longer
  commits its writes. It joined the outer transaction, whose commit ignored
  the action's rollback, so a recorded Failure still committed its rows
  (measured on ActiveRecord 8.1 + SQLite). Inside an open transaction the action
  now takes its own savepoint (requires_new: true) unless requires_new: is
  given; requires_new: false keeps the old joining behaviour.

• A nested action no longer wipes parent ivars it never set. Absorbing a
  successful or skipped child copied every declared output field, so a field
  the child left nil (or at its default) overwrote the parent's value. Only
  fields the child actually set are absorbed now; expose: still narrows them.

• Private step, hook and case_step methods work. The definition check
  already accepted them, but the step then raised NoMethodError; they are
  now called like guards are. A step or hook named after a method the action
  only inherits from Ruby's core (step :puts, always :exit) raises
  DefinitionError up front instead of calling Kernel.

• Action.input without a block reads the schema instead of replacing it
  with an empty one, matching output.

• A step that assigns @result gets a clear DefinitionError instead of a
  NoMethodError deep in the runner.

• History#to_json requires Oj itself rather than relying on another file
  having loaded it.

• A bang verb inside a lifecycle hook now sets the result. fail!,
  skip! or succeed! in a hook used to be dropped: fail! in on_success
  returned Success, committed a transactional action and acked the job.
  The hook's result is now adopted before the halt stops the remaining hooks,
  as the docs always said. This includes a nested action used as a hook
  (on_success ChildAction): a failing child now fails the run and stops the
  remaining hooks.

• succeed/skip kwargs survive lifecycle hooks. After any hook
  refreshed the output, the kwargs were lost: a required field set only by
  kwarg turned the run into Failure(:invalid_output), and a kwarg that
  overrode an ivar silently reverted to the ivar's value. Present since 1.0.0.
  A Failure(:invalid_output) also keeps the output that failed validation
  across hooks instead of having it rebuilt from ivars.

• No spurious errors[:output] on a failure or skip. The best-effort,
  unvalidated output of a non-typed failure or skip added
  output: ["is invalid"] to the result's errors. It no longer does; errors
  the failure recorded itself are kept.