fix: apply Dodge to every Dexterity save

[dajiaohuang]

Closes #131.

What changed

• derive Dexterity-save advantage from the authoritative encounter combatant in the shared domain resolver
• reuse the Dodge lifecycle helper introduced by fix: end invalid Dodge benefits permanently #142, including effective-speed and incapacitation handling
• route structured spells, generic combat checks, content activities, semantic saves, and area save-damage settlement through that encounter-aware resolver
• normalize ability aliases/casing/whitespace before matching and retain the Dodge rule receipt when advantage and disadvantage cancel

Validation

• full domain test suite
• full modified MCP test files for combat transactions, structured spells, and agent save damage
• focused generic-save, Fireball, Dragonborn Breath, area-save, CAS, idempotency, random-stream, no-write, and Dodge lifecycle coverage
• Core rule-pack and official-expansion lock tests
• ruff check packages/domain packages/mcp
• git diff --check