## Description
Extracts the sticky CCR session tracker from `headroom.proxy.helpers`
into a focused state module. `helpers.SessionCcrTracker` remains as an
env-aware compatibility wrapper so existing CCR tool injection and
singleton call sites keep the same API.
Closes #
## Type of Change
- [ ] Bug fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
- [ ] Performance improvement
- [x] Code refactoring (no functional changes)
## Changes Made
- Added `headroom.proxy.ccr_session_tracker.SessionCcrTracker` as the
pure bounded LRU CCR state holder.
- Replaced the in-helper CCR tracker implementation with a small
env-aware wrapper.
- Added direct tracker tests for unknown sessions, monotonic done state,
first-write golden bytes, provider isolation, LRU eviction, reset, and
input validation.
## Testing
- [x] Unit tests pass (`pytest`)
- [x] Linting passes (`ruff check .`)
- [x] Type checking passes (`mypy headroom`)
- [x] New tests added for new functionality
- [ ] Manual testing performed
### Test Output
```text
python -m pytest tests/test_ccr_session_tracker.py tests/test_ccr_tool_always_on.py tests/test_corrupt_golden_bytes_recovery.py tests/test_issue_728_empty_tools_injection.py
35 passed in 0.69s
python -m ruff check .
All checks passed!
python -m ruff format --check .
1069 files already formatted
python -m mypy headroom --ignore-missing-imports
Success: no issues found in 410 source files
gitleaks protect --staged --no-banner --redact
no leaks found
```
## Real Behavior Proof
- Environment: Windows, Python 3.13.13
- Exact command / steps: Ran direct CCR tracker tests, CCR always-on
tests, corrupt golden byte recovery tests, empty tools injection
regression tests, full ruff, format check, mypy, and staged gitleaks
scan.
- Observed result: Existing sticky CCR tool behavior and recovery
behavior remain green while the CCR session state domain is directly
covered.
- Not tested: Full repository pytest suite locally; CI covers the
broader matrix.
## Review Readiness
- [x] I have performed a self-review
- [x] This PR is ready for human review
## Checklist
- [x] My code follows the project's style guidelines
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] I have updated the CHANGELOG.md if applicable
## Screenshots (if applicable)
N/A
## Additional Notes
Documentation and changelog updates are not applicable for this internal
refactor. The default-branch Dependabot alerts reported during push are
pre-existing and unrelated to this PR.
