refactor(state): split server state modules

Author: haasonsaas

TODO.md

@@ -127,7 +127,7 @@ This roadmap is derived from deep research into Greptile's public docs, blog, MC
 ## 9. Infra, Self-Hosting, and Enterprise Operations
 
 81. [x] Split `src/server/api.rs` by domain so the growing platform API stays maintainable.
-82. [ ] Split `src/server/state.rs` into session lifecycle, persistence, progress, and GitHub coordination modules.
+82. [x] Split `src/server/state.rs` into session lifecycle, persistence, progress, and GitHub coordination modules.
 83. [x] Add queue depth and worker saturation metrics for long-running review and eval jobs.
 84. [ ] Add retention policies for review artifacts, eval artifacts, and trend histories.
 85. [x] Add storage migrations for richer comment lifecycle and reinforcement schemas.