[Richard Lundeen (richlundeen)]

Description

Complete the remaining simplifications from the Simplifying Scenarios plan, following #2132. The two historical adaptive bugs were already fixed in #2152; this PR preserves their regression coverage rather than introducing another fix. The biggest change is to modify initializer paramaters to match other registries like scenarios and converters/targets/etc.

Here is a list of changes:

• Use classmethod parameter declarations and the shared typed resolver for initializers. Separate configuration from validation, so startup checks do not replace the configured parameter bag or its values.
• Support required scalar/list inputs without blocking no-argument construction or metadata discovery. Reject missing required inputs when configuration is complete.
• Reject fractional integer conversions instead of truncating them. In particular, YAML days: 0.5 or days: -0.5 cannot become days: 0 and trigger unconditional dataset refresh.
• Pass common construction inputs through ScenarioContext, including nested manual builders and per-technique converters. Copy converter containers while retaining live converter instances by identity. Keep scenario-specific scorers and options on the scenario.
• Reuse the existing registry configuration helper for estimates with cancellation-safe construction ownership. Read the stored scenario result once during resume.
• Correct the adaptive guide: technique choices use historical results during initialization, are saved in the run plan, and are replayed on resume. Execution stops on success; it does not reselect based on earlier objectives in the same prebuilt run.

Breaking change and migration: custom initializers must change supported_parameters from an instance property to a classmethod, declare parameter types, and read typed scalar values rather than indexing string lists. Use set_params_from_args to configure inputs instead of assigning raw or partial parameter dictionaries. validate_params() checks resolved values without coercing or repairing them. CLI/YAML syntax is unchanged. Fractional values supplied for integer parameters now raise an error rather than truncate. These changes remove separate parsing and configuration mechanisms; no generic builder framework, new dependency, lockfile change, or persistence migration is included.