Migration from core/go pkg/i18n

Context

core/go/pkg/i18n was the original i18n implementation bundled inside the monolith. It has been partially extracted to go-i18n but the extraction is incomplete.

What Migrates vs What Stays

Migrates to go-i18n (already done)

• Grammar primitives (PastTense, Gerund, Pluralize, Article)
• Irregular verb/noun databases
• Handler chain pattern (i18n.* namespace magic)
• Service + message lookup
• Subject builder
• Number/time formatting
• Plural categories (CLDR)
• RTL/LTR support

Stays in core/go (to be removed)

• 34 locale files — bad data, needs full rework, NOT migrated
• CLI integration wrapper — belongs in core/cli, not go-i18n
• Completeness validation tool — CLI-specific, not library concern

Key Principle

go-i18n is a grammar engine, not a translation file manager.

Consumers (core/cli, apps) bring their own translation files. go-i18n provides:

1. Grammar primitives for composing grammatically correct text
2. Reversal engine for extracting grammar structure
3. GrammarImprint for privacy-preserving classification
4. Training data multiplier for augmentation

It does NOT ship, manage, or validate consumer translation files.

Steps to Complete Migration

1. core/cli imports forge.lthn.ai/core/go-i18n instead of pkg/i18n
2. core/cli manages its own locale files (fresh, not copied from bad data)
3. core/go removes pkg/i18n/ entirely
4. core/go go.work includes go-i18n for local dev