The 1864-line story_tools.rs is split into:
- story.rs: story creation/lifecycle/management (903 lines incl. tests)
- criteria.rs: acceptance-criteria tools (534 lines)
- bug.rs: bug item tools (318 lines)
- spike.rs: spike item tools (120 lines)
- refactor.rs: refactor item tools (60 lines)
- mod.rs: re-exports (25 lines)
Tests stay co-located with the code they exercise; setup_git_repo_in and
setup_story_for_update test helpers are duplicated into the modules that need
them rather than centralised, since they are tiny and test-only.
No behaviour change. All 60 story_tools tests pass; full suite green
(2635 tests with --test-threads=1).
dave