observability

Write and review Swift code that makes an app observable: emit the right signal (log, signpost, metric, diagnostic) at the right level, keep user data out of the logs, and get the data back from production in a form you can actually read - symbolicated, aggregated, and attributed to the right release.

Review process:

1. Establish the signal model (three pillars, unified logging architecture, levels and persistence, dev vs production visibility) using references/fundamentals.md.
2. Confirm each emission uses the right signal via the decision tree below; reroute if it does not (print where a Logger belongs, a log where a signpost belongs, a hand-rolled timer where MetricKit already measures).
3. Validate Logger usage (subsystem/category structure, level choice, privacy annotations, interpolation performance, wrapper design) using references/logger-api.md.
4. Validate log retrieval workflows (Console.app, log CLI predicates, logging profiles, sysdiagnose) using references/log-cli-and-console.md.
5. Validate in-app log access and support-log export using references/oslogstore.md.
6. Validate signpost instrumentation (OSSignposter, IDs, intervals, points of interest, Instruments wiring) using references/signposts.md.
7. Validate cross-flow correlation (activities, correlation IDs) using references/activity-tracing.md.
8. Validate MetricKit adoption (subscription timing, payload handling, histograms, diagnostics, the iOS 27 MetricManager API) using references/metrickit.md.
9. Validate crash/hang/OOM observability (what leaves a report and what does not, exit reasons, Organizer) using references/crash-reporting.md.
10. Validate symbolication (dSYM handling, UUID matching, atos, MetricKit call stacks) using references/symbolication.md.
11. Validate the production pipeline (export format, units, aggregation strategy, launch-metric skew, alerting) using references/production-monitoring.md.
12. Validate network-request observability (error taxonomy and noise filtering, non-fatal report design, URLSessionTaskMetrics, aggregate monitoring) using references/network-telemetry.md.
13. Validate third-party SDK integration (crash-handler exclusivity, dSYM upload, bridging, privacy) using references/third-party-sdks.md.
14. Catch common mistakes using references/anti-patterns.md.