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.

src/everos/infra/persistence/markdown/mds/atomic_fact.py

@@ -0,0 +1,38 @@
+"""AtomicFact frontmatter — daily-log markdown for user-scoped atomic facts.
+
+Path: ``users/<scope_id>/.atomic_facts/atomic_fact-<YYYY-MM-DD>.md``.
+
+The directory is dot-prefixed so it is hidden from end users (same
+convention as ``.index``); atomic facts are framework-internal derived md,
+not material the user is expected to read by hand.
+
+Each entry carries one atomic fact extracted by the algo layer; the fact
+always hangs off the source MemCell (see ``parent_type`` in each entry's
+inline fields — handled at the StructuredEntry layer, not on the
+file-level frontmatter).
+"""
+
+from __future__ import annotations
+
+import datetime as _dt
+from typing import ClassVar, Literal
+
+from everos.core.persistence.markdown import (
+    DailyLogPathMixin,
+    UserScopedFrontmatter,
+)
+
+
+class AtomicFactDailyFrontmatter(DailyLogPathMixin, UserScopedFrontmatter):
+    """Frontmatter for ``users/<scope>/.atomic_facts/atomic_fact-<YYYY-MM-DD>.md``."""
+
+    ENTRY_ID_PREFIX: ClassVar[str] = "af"
+    DIR_NAME: ClassVar[str] = ".atomic_facts"
+    FILE_PREFIX: ClassVar[str] = "atomic_fact"
+
+    type: Literal["atomic_fact_daily"] = "atomic_fact_daily"
+    file_type: Literal["atomic_fact_daily"] = "atomic_fact_daily"
+    date: _dt.date
+    entry_count: int = 0
+    created_at: _dt.datetime | None = None
+    last_appended_at: _dt.datetime | None = None