* fix(crash-reporting): decode POSIX wait statuses for display and record Windows session-end reasons
Chromium on POSIX hands render/child-process-gone the raw waitpid() status, so
crash reports read "Exit code: 61696" where exit status 241 is meant (field:
61696=exit 241, 9=SIGKILL, 133=SIGTRAP+core, darwin crashed 5=SIGTRAP). Decode
at the display layer only: the stored exitCode stays raw, Windows codes and
launch-failed launch-error codes render unchanged, and the process-gone span
gains a crash.exit_code_decoded attribute.
Also durably record a system_session_end breadcrumb (with WindowSessionEndEvent
reasons) when Windows session-end fires, so bundles can tell OS shutdown from a
user task-kill in killed/exit-1 sweeps.
* test(crash-reporting): pin the exit(0) no-suffix rendering
Adversarial mutation review: removing the exit-0 suppression in
formatCrashReportExitCode survived the suite — nothing pinned that a clean
exit(0) renders without an '(exit status 0)' suffix.
* test(crash-reporting): decode-attribute tests use synchronous child kills
Renderer killed events gain a 250ms sibling-kill settle once the
correlation branch lands, which (a) defers the span past the test's
platform stub so the decode gate reads the real host platform, and (b)
adds a deferred span that breaks the exact sink assertion. The decode
gate is source-agnostic, and a non-recoverable child kill persists
synchronously on every branch of the stack, so coverage is unchanged and
the platform stub is deterministic on any CI host.
* fix(crash-reporting): keep session-end reasons type-safe
