[config] Wire ProfileConfig into ContextManager, Router, and TreeBuilder

[dgenio]

Context

Split from #45. Wires ProfileConfig into ContextManager, Router, and TreeBuilder so users can pass a single config object.

Depends on the presets child issue (ProfileConfig must exist first).

Acceptance Criteria

• ContextManager gains optional profile: ProfileConfig | None parameter that pre-fills budget, policy, scoring
• Router gains optional routing_config: RoutingConfig | None parameter as alternative to individual kwargs
• TreeBuilder gains optional routing_config: RoutingConfig | None parameter for max_children/target_group_size
• Individual kwargs still work (backward-compatible)
• ProfileConfig kwargs override individual kwargs when both are provided (with clear precedence)
• Tests for ProfileConfig integration path

File Paths

• src/contextweaver/context/manager.py (edit)
• src/contextweaver/routing/router.py (edit)
• src/contextweaver/routing/tree.py (edit)
• tests/test_config.py (edit)
• tests/test_manager.py (edit)

Parent Issue

Part of #45 (ProfileConfig).