docs(P01): complete minimal-voice-loop phase

---ci---
phase: 1
milestone: v0.1
status: complete
requirements:
  covered: [REQ-VOICE-01, REQ-VOICE-02, REQ-VOICE-03, REQ-VOICE-04, REQ-SCEN-01, REQ-STATE-01, REQ-LLM-01, REQ-LLM-02, REQ-DEBRIEF-01, REQ-ORCH-01, REQ-ORCH-02, REQ-SCEN-FMT-01, REQ-NFR-LAT-01, REQ-NFR-SAFE-01, REQ-NFR-COST-01]
  partial: []
---/ci---

db/migrate.py

@@ -0,0 +1,46 @@
+"""SQLite migration runner — applies db/migrations/*.sql in order."""
+
+from __future__ import annotations
+
+import sqlite3
+from pathlib import Path
+
+_DEFAULT_DB_PATH = Path("praxis.db")
+_DEFAULT_MIGRATIONS_DIR = Path(__file__).resolve().parent / "migrations"
+
+
+def apply_migrations(
+    db_path: Path | str | None = None,
+    migrations_dir: Path | None = None,
+) -> list[str]:
+    """Apply all pending migrations in order. Returns the list of applied names.
+
+    Uses a `_migrations` tracking table so re-running is idempotent.
+    """
+    db = Path(db_path) if db_path else _DEFAULT_DB_PATH
+    mdir = migrations_dir or _DEFAULT_MIGRATIONS_DIR
+
+    conn = sqlite3.connect(str(db))
+    try:
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS _migrations (id TEXT PRIMARY KEY, applied_at TEXT NOT NULL DEFAULT (datetime('now')))"
+        )
+        applied: list[str] = []
+        for sql_path in sorted(mdir.glob("*.sql")):
+            mid = sql_path.stem
+            already = conn.execute(
+                "SELECT 1 FROM _migrations WHERE id = ?", (mid,)
+            ).fetchone()
+            if already:
+                continue
+            sql = sql_path.read_text(encoding="utf-8")
+            conn.executescript(sql)
+            conn.execute("INSERT INTO _migrations (id) VALUES (?)", (mid,))
+            conn.commit()
+            applied.append(mid)
+        return applied
+    finally:
+        conn.close()
+
+
+__all__ = ["apply_migrations"]