docs(releases): rewrite 3.0.0 release notes for narrative clarity

- Reorganize features into logical groups: Statecharts, Invoke, Event
  dispatch, Error handling, New API, Developer experience
- Move compound/parallel states before Invoke (conceptual dependency)
- Group delayed events, raise_(), cancel_event(), send() params under
  Event dispatch section
- Add missing features: constructor kwargs forwarding, self-transition
  entry/exit behavior, validation flags, In(state) with parallel example
- Replace broken Bugfixes/Misc placeholders removal
- Compact backward-incompatible changes into summary list with link to
  upgrade guide (avoids duplication)
- Fix typos: Dinamically, versios, exiting, recomend, usefull
- Convert non-testable delayed event examples to plain python blocks
  (sync engine blocks on delay)
- Add missing cross-reference links to docs pages
- Add blocking delay note to statechart.md delayed events section

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: fgmacedo