Completes the wait capability per review guidance ("add corresponding
execution hooks and fallback tests for the modes"):
- contract.WaitSpec restores event/auto modes with event_key,
match_field, and a new resource_query (dotted path into the accepted
result data yielding the identifier events correlate against);
per-mode validation of required fields
- internal/wait adds EventStream (leaf-owned transport) and RunEvent:
correlated-event filtering, the same terminal/pending/unknown mapping
as polling, timed-out pending on deadline during consumption, and an
ErrEventStreamEnded sentinel distinguishing stream termination from
fail-closed status errors
- Spec.WaitEvents hook; validateWaitDecl pairs mode with hooks
(poll<->WaitPoll, event<->WaitEvents, auto<->both; surplus hooks
rejected too)
- the wait phase runs event-first in auto mode and falls back to polling
when the stream ends or the subscription fails, under one deadline
spanning both phases; strict event mode surfaces stream errors
- output.CommandResult gains Data() (deep copy) so the framework can
resolve the resource identifier without exposing mutable state
Changed-code coverage re-verified at 100% (CI cross-package recipe).