Custom Scenario Authoring

Allow controllers to save the current state of a session as a custom scenario for future reuse. A Save as Scenario button on the controller opens a small form: scenario name, scenario group (from the existing 12 groups or a Custom group), patient population, and brief clinical context note. On save, the system serializes all current vital values, rhythm, ectopy, capnography waveform, threshold preset, and pleth parameters into a scenario object using the same data model as system scenarios (the v1 spec includes a system: true/false flag for this). Saved scenarios appear in the scenario library modal in a My Scenarios group, accessible to that controller. v1.5 ships with author-only access. Future releases will add scenario sharing via export/import (JSON) and shareable links.