feat(harness): persist server sessions in postgres

harness/tht/cli/session_cmd.py

@@ -9,6 +9,39 @@ from tht.cli.schema_cmd import _load_config_or_exit
 session_app = typer.Typer(help="Sessioni (directory artefatti)")
 
 
+@session_app.command("migrate")
+def migrate_cmd(
+    database_url: str = typer.Option(
+        ..., "--database-url", envvar="THT_SESSIONS_ADMIN_URL", help="Admin PostgreSQL URL."
+    ),
+    status_only: bool = typer.Option(False, "--status", help="Inspect without applying."),
+    json_output: bool = typer.Option(False, "--json", help="Emit pristine JSON."),
+) -> None:
+    """Apply or inspect the private PostgreSQL session schema migrations."""
+    from tht.session.postgres_repository import MigrationError, migrate, migration_status
+
+    try:
+        status = migration_status(database_url) if status_only else migrate(database_url)
+    except (MigrationError, ValueError) as exc:
+        if json_output:
+            typer.echo(json.dumps({"error": str(exc)}, sort_keys=True))
+        else:
+            typer.echo(f"ERROR: {exc}", err=True)
+        raise typer.Exit(code=1) from None
+    payload = {
+        "applied": [item.version for item in status.applied],
+        "drifted": [item.version for item in status.drifted],
+        "pending": [item.version for item in status.pending],
+    }
+    if json_output:
+        typer.echo(json.dumps(payload, sort_keys=True))
+    else:
+        typer.echo(
+            f"Applied: {len(status.applied)}; pending: {len(status.pending)}; "
+            f"drifted: {len(status.drifted)}"
+        )
+
+
 def session_dir(cfg, session_id: str) -> Path:
     return cfg.paths.sessions / session_id