Foundation package with zero external dependencies. Implements 3-tier
AIPASS_ROOT resolution: env var → .aipass/ marker walk → ~/.aipass/ default.
Includes derived path helpers (system_logs_dir, branch_registry_path,
branch_path, branch_logs_dir). 32 tests, full coverage.
Also positions placeholder modules (cortex, mail, prax) with documented
intent for upcoming implementation. Version bumped to 1.0.0.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>