[FEATURE] Measure docs entry to first successful AURA run #408

Outcome

AURA can measure whether the onboarding journey achieves its initiative-level job: a successful run against real data within five minutes of entering the getting-started flow.

Scope

• Define the start event as entry to the primary getting-started journey.
• Define a successful completion event that represents a real AURA run, not merely installation or process launch.
• Report median elapsed time and the major funnel drop-off points.
• Use privacy-preserving, opt-out run telemetry supplied by [INITIATIVE] Adoption Measurement #431 for the product-side completion signal.
• Keep distribution-surface counts from [FEATURE] Report install adoption by distribution channel #406 available as a separate input so package download and product-run drop-off are not conflated.
• Document the effect of telemetry-disabled installs and any inability to join anonymous events.

Acceptance criteria

• The team has a documented metric definition, event boundaries, exclusions, and owner.
• A repeatable report shows journey entries, successful runs, conversion, and median time-to-success.
• Results can be segmented by supported install path where the underlying aggregate data permits.
• The implementation does not require identifying individual users.

Dependency: #431 Adoption Measurement
Related: #406
Parent epic: #311
Initiative: #370