chore: initialize EverOS 1.0.0

md-first memory extraction framework for AI agents.

Markdown is the single source of truth; SQLite holds state and LanceDB
provides the rebuildable vector + BM25 + scalar index. The codebase follows
a single-direction DDD layering (entrypoints -> service -> memory -> infra,
with component / core / config cross-cutting) enforced by import-linter.

Engineering surface:
- Coding conventions in .claude/rules/ (path-scoped) and workflows in
  .claude/skills/ (/commit, /new-branch, /pr).
- GitHub Actions CI runs make lint + test + integration; pre-commit mirrors
  the gates locally (ruff, hygiene hooks, gitlint commit-msg).
- Commit messages follow Conventional Commits, enforced by gitlint.
- make lint also enforces datetime two-zone discipline and OpenAPI drift.

tests/unit/test_component/test_llm/test_client.py

@@ -0,0 +1,64 @@
+"""get_llm_client — raises on missing credentials, caches on success."""
+
+from __future__ import annotations
+
+import importlib
+
+import pytest
+from pydantic import SecretStr
+
+from everos.component.llm import LLMNotConfiguredError
+from everos.config import Settings
+from everos.config.settings import LLMSettings
+
+_client_mod = importlib.import_module("everos.component.llm.client")
+
+
+def _reset_singleton(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(_client_mod, "_llm_client", None, raising=False)
+
+
+def _patch_settings(
+    monkeypatch: pytest.MonkeyPatch,
+    *,
+    api_key: str | None,
+    base_url: str | None,
+) -> None:
+    """Stub the ``load_settings`` reference bound inside the client module."""
+    cfg = Settings(
+        llm=LLMSettings(
+            model="gpt-4o-mini",
+            api_key=SecretStr(api_key) if api_key is not None else None,
+            base_url=base_url,
+        )
+    )
+    monkeypatch.setattr(_client_mod, "load_settings", lambda: cfg)
+
+
+def test_raises_when_api_key_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    _reset_singleton(monkeypatch)
+    _patch_settings(monkeypatch, api_key=None, base_url="https://example.test")
+
+    with pytest.raises(LLMNotConfiguredError, match="EVEROS_LLM__API_KEY"):
+        _client_mod.get_llm_client()
+
+
+def test_raises_when_base_url_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    _reset_singleton(monkeypatch)
+    _patch_settings(monkeypatch, api_key="sk-test", base_url=None)
+
+    with pytest.raises(LLMNotConfiguredError, match="EVEROS_LLM__BASE_URL"):
+        _client_mod.get_llm_client()
+
+
+def test_returns_singleton_when_configured(monkeypatch: pytest.MonkeyPatch) -> None:
+    _reset_singleton(monkeypatch)
+    _patch_settings(monkeypatch, api_key="sk-test", base_url="https://example.test")
+    sentinel = object()
+    monkeypatch.setattr(_client_mod, "build_client", lambda cfg: sentinel)
+
+    first = _client_mod.get_llm_client()
+    second = _client_mod.get_llm_client()
+
+    assert first is sentinel
+    assert first is second