Core.Mood — re-export hub

Imports the three mood-category files so that downstream code can write import Linglib.Core.Mood instead of cherry-picking each subfile.

The split mirrors mathlib's "one concept per file" discipline:

• Core/Mood/Basic.lean — GramMood (indicative/subjunctive), SubjunctiveType, MoodEffect
• Core/Mood/IllocutionaryMood.lean — IllocutionaryMood (declarative/interrogative/imperative/promissive/exclamative) + moodAuthority
• Core/Mood/ClauseType.lean — ClauseType = IllocutionaryMood × GramMood, bridge from UD.Mood

The pragmatic-act extensions of force (Searle classes, direction of fit, preparatory conditions) live in Core/Discourse/IllocutionaryForce.lean because they are pragmatic-theoretic, not mood-categorial. The DiscourseRole (speaker/addressee) lives in Core/Discourse/Roles.lean.