Adds wide-event observability for the supervisor: one flat-keyed JSON
line per dequeue iteration, workload-server route, and run socket
lifecycle event. Events carry `trace_id` sourced from the inbound W3C
traceparent plus `meta.run_id` and related identifiers, so they join
across services by run.
The outbound warm-start POST also forwards the inbound traceparent so
the upstream receiver continues the same trace instead of minting a new
one.
Off by default behind `TRIGGER_WIDE_EVENTS_ENABLED`. With the flag off,
no events are emitted, no ALS state is allocated, and the outbound
warm-start request is unchanged — every call site was audited to confirm
the off path is byte-identical to current behavior.
Dequeue-path phase timings recorded under `phase.<name>.duration_ms`:
`restore`, `warm_start`, `workload_create`. A `path_taken` extra
distinguishes `restore` / `warm_start` / `cold_create` /
`skipped_no_image`.
Refs TRI-9480.
nicktrn
d541caeb5e