feat(mem0-plugin): smart retrieval, citations, pre-commit capture (Tier 7)

Smart retrieval tier:
- on_user_prompt.sh: stack-trace detection (auto-searches anti_patterns on errors)
- on_user_prompt.sh: file-aware retrieval (extracts file paths, suggests scoped search)
- on_user_prompt.sh: recency boost guidance for state-related queries
- mem0-mcp/SKILL.md: inline citation format [mem0:<8char_id>]
- on_pre_commit.py: captures staged diff as commit_context memory via REST API

mem0-plugin/tests/test_pre_commit.py

@@ -0,0 +1,54 @@
+"""Tests for on_pre_commit.py — pre-commit memory capture."""
+
+from __future__ import annotations
+
+import os
+from unittest.mock import MagicMock
+
+SCRIPTS_DIR = os.path.join(os.path.dirname(__file__), "..", "scripts")
+
+
+def test_import_succeeds():
+    """on_pre_commit module can be imported."""
+    import on_pre_commit
+
+    assert hasattr(on_pre_commit, "main")
+
+
+def test_no_api_key_exits_zero(monkeypatch):
+    """main() exits 0 when no API key is set."""
+    import on_pre_commit
+
+    monkeypatch.delenv("MEM0_API_KEY", raising=False)
+    monkeypatch.delenv("CLAUDE_PLUGIN_OPTION_MEM0_API_KEY", raising=False)
+    monkeypatch.setattr("sys.stdin", MagicMock(isatty=lambda: True))
+
+    assert on_pre_commit.main() == 0
+
+
+def test_empty_diff_exits_zero(monkeypatch):
+    """main() exits 0 when stdin diff is empty."""
+    from io import StringIO
+
+    import on_pre_commit
+
+    monkeypatch.setenv("MEM0_API_KEY", "test-key")
+    monkeypatch.setattr("sys.stdin", StringIO(""))
+
+    assert on_pre_commit.main() == 0
+
+
+def test_get_staged_summary_runs():
+    """get_staged_summary doesn't crash even outside a git repo."""
+    import on_pre_commit
+
+    result = on_pre_commit.get_staged_summary()
+    assert isinstance(result, str)
+
+
+def test_get_commit_message_runs():
+    """get_commit_message doesn't crash even outside a git repo."""
+    import on_pre_commit
+
+    result = on_pre_commit.get_commit_message()
+    assert isinstance(result, str)