test: comprehensive test suite

Unit tests:
- test_security_boundaries.py: vault block, vault lock sentinel
- test_security_injection.py: all 4 injection categories, case-insensitive
- test_vault_rw.py: roundtrip, file permissions (chmod 400), no key in config
- test_config.py: schema roundtrip, no api_key field, chmod 600 on config.yaml
- test_memory_reader.py: list, read, sandboxing, context loading
- test_memory_writer.py: write, append, index update, traversal blocked, chmod 600
- test_providers.py: required fields, unique IDs, litellm prefix format
- test_renderer.py: key redaction for sk-ant-, sk-, AIza patterns

Security tests:
- test_vault_ai_isolation.py: 7 traversal patterns blocked via memory read/write
- test_path_traversal.py: 20+ traversal patterns — all rejected for read and write
- test_prompt_injection.py: 21-item corpus + 5 clean texts (no false positives)

Integration tests:
- test_lmstudio.py: live call to localhost:1234, streaming, full stack session,
  injection scan on real output (skips if LM Studio not running)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/test_security_boundaries.py

@@ -0,0 +1,40 @@
+import pytest
+from pyra.security.boundaries import VaultAccessError, PyraSecurityError, assert_safe_path
+
+
+def test_vault_path_blocked(tmp_pyra_home):
+    from pyra.security.boundaries import VAULT_PATH
+    with pytest.raises(VaultAccessError):
+        assert_safe_path(VAULT_PATH / "secrets" / "api_keys.json")
+
+
+def test_vault_root_blocked(tmp_pyra_home):
+    from pyra.security.boundaries import VAULT_PATH
+    with pytest.raises(VaultAccessError):
+        assert_safe_path(VAULT_PATH)
+
+
+def test_memory_path_allowed(tmp_pyra_home):
+    memory_path = tmp_pyra_home / "memory" / "user" / "profile.md"
+    memory_path.parent.mkdir(parents=True, exist_ok=True)
+    memory_path.touch()
+    assert_safe_path(memory_path)  # must not raise
+
+
+def test_config_path_allowed(tmp_pyra_home):
+    config = tmp_pyra_home / "config.yaml"
+    config.touch()
+    assert_safe_path(config)  # must not raise
+
+
+def test_check_vault_lock_passes(tmp_pyra_home):
+    from pyra.security.boundaries import check_vault_lock
+    check_vault_lock()  # sentinel exists, must not raise
+
+
+def test_check_vault_lock_fails_when_missing(tmp_pyra_home):
+    from pyra.security.boundaries import check_vault_lock
+    lock = tmp_pyra_home / "vault" / ".vault_lock"
+    lock.unlink()
+    with pytest.raises(PyraSecurityError):
+        check_vault_lock()