Add five behave scenarios exercising the previously-uncovered error
branches in AdaptiveContextSelector (select_strategy and
select_strategies with an unconfigured plan_type) and ContextFusion
(fuse_results and fuse_with_selector with an unconfigured plan_type),
plus a scenario constructing a valid-weight StrategyWeight to cover
the success path of the field_validator.
ISSUES CLOSED: #5255
Implements adaptive context strategy selector that chooses the best context
strategy based on plan type, and context fusion that combines results from
multiple strategies with configurable weights.
Features:
- AdaptiveContextSelector: Intelligent strategy selection per plan type
- ContextFusion: Weighted combination of multiple strategy results
- PlanType enumeration: coding, analysis, documentation, refactoring, testing, debugging
- AdaptiveStrategyConfig: YAML-compatible configuration for strategy selection
- FusedResult: Ranked file list with strategy contributions and metadata
- Full type annotations and comprehensive Behave BDD tests
Closes#5255