Refactor store.rs to reduce size and consolidate repetitive logic/tests

**Problem:**
The `store.rs` file is getting too large, making it harder to navigate and maintain. The implementation and tests contain repetitive logic and logically duplicated test cases, which increases cognitive load and makes the file unnecessarily large.

**Task:**
- [ ] Audit `store.rs` to identify repetitive implementation logic.
- [ ] Extract reusable helpers or modules to consolidate repeated patterns.
- [ ] Identify and merge logically duplicated test cases.
- [ ] Reorganize tests to improve clarity and reduce redundancy.
- [ ] Verify that all existing behavior remains unchanged after refactoring.

**Acceptance Criteria:**
- [ ] `store.rs` is significantly reduced in size or split into smaller, focused modules.
- [ ] Repetitive logic in the implementation is consolidated into reusable helpers.
- [ ] Logically duplicated test cases are merged or removed.
- [ ] All existing tests continue to pass.
- [ ] No functional behavior changes are introduced.

Read `store.rs` first, including its test section, because the issue explicitly targets repetitive implementation and test logic there. Next, map repeated patterns and duplicated cases to propose reusable helpers or module splits while keeping behavior unchanged. Run the project test suite to verify nothing regressed; completion is a reduced/split `store.rs` plus merged or removed redundant tests with all existing tests still passing.

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