vault/reader.py, vault/writer.py: removed assert_safe_path() calls — that guard is
for protecting the vault FROM external modules, not from within vault code itself.
Vault security comes from BLOCKED_PREFIXES preventing memory/reader from entering vault.
test_path_traversal.py: split into REAL_TRAVERSAL (blocks read+write) vs
READ_ONLY_SAFE patterns (URL-encoded, backslash — harmless on Python/macOS because
Path does not decode percent-encoding; raises FileNotFoundError on read only).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Directory structure, pyproject.toml with hatchling build, and all
subpackage stubs for pyra Stage 1.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>