StorageProvider: Phase 3 — CLI migration to SquadState APIs

[diberry]

Context

PRD bradygaster#481 Phase 3: Replace all CLI raw string surgery with SquadState typed APIs.

Problem

The CLI currently writes .squad/ files via raw string concatenation — no type safety, no serialization, prone to format drift.

Expected

All CLI write operations use SquadState APIs instead of direct fs/string manipulation.

Scope

• Replace CLI decision writing with state.decisions.add()
• Replace CLI agent creation with state.agents.create()
• Replace CLI team.md updates with state.team.update()
• Replace CLI routing updates with state.routing.update()

Dependencies

• Phase 2 complete (done)
• Empty fields issue and missing collections issue should be addressed first

Source

PRD bradygaster#481

[diberry]

Completed in PR #18 (StorageProvider Phases 0-3 + Waves 3a/3b/3c/4).