refactor(sync): extract stats-sync engine behind a DB-driver interface

Move snapshot/merge/quiescence engine and ssh helpers from launcher/sync
into src/core/services/stats-sync, parameterized on a minimal SyncDb
driver. The launcher binds it to bun:sqlite via launcher/sync/bun-driver;
the sync command becomes a thin adapter over the shared sync flow.

launcher/sync/ssh.ts

@@ -1,106 +1,10 @@
-import { spawnSync } from 'node:child_process';
-
-export interface RemoteRunResult {
-  status: number;
-  stdout: string;
-  stderr: string;
-}
-
-/**
- * ssh/scp have no `--` terminator for the destination, so a host that starts
- * with `-` (e.g. `-oProxyCommand=...`) is parsed as an option. Reject those
- * before spawning.
- */
-export function assertSafeSshHost(host: string): void {
-  if (host.startsWith('-')) {
-    throw new Error(`Refusing to use SSH host that looks like an option: ${host}`);
-  }
-}
-
-/**
- * Run a command on the SSH host. stdin stays attached so interactive prompts
- * can still read from the terminal; stdout/stderr are captured for callers
- * that need actionable remote failure messages.
- */
-export function runSsh(host: string, remoteCommand: string): RemoteRunResult {
-  assertSafeSshHost(host);
-  const result = spawnSync('ssh', [host, remoteCommand], {
-    encoding: 'utf8',
-    stdio: ['inherit', 'pipe', 'pipe'],
-  });
-  if (result.error) {
-    throw new Error(`Failed to run ssh: ${(result.error as Error).message}`);
-  }
-  return { status: result.status ?? 1, stdout: result.stdout ?? '', stderr: result.stderr ?? '' };
-}
-
-function assertSafeScpEndpoint(endpoint: string): void {
-  const colon = endpoint.indexOf(':');
-  const slash = endpoint.indexOf('/');
-  if (colon <= 0 || (slash !== -1 && slash < colon)) {
-    if (endpoint.startsWith('-')) {
-      throw new Error(`Refusing to use scp endpoint that looks like an option: ${endpoint}`);
-    }
-    return;
-  }
-
-  const host = endpoint.slice(0, colon);
-  const remotePath = endpoint.slice(colon + 1);
-  assertSafeSshHost(host);
-  if (remotePath.startsWith('-')) {
-    throw new Error(`Refusing to use scp remote path that looks like an option: ${remotePath}`);
-  }
-}
-
-export function runScp(from: string, to: string): void {
-  assertSafeScpEndpoint(from);
-  assertSafeScpEndpoint(to);
-  const result = spawnSync('scp', ['-q', from, to], {
-    encoding: 'utf8',
-    stdio: ['inherit', 'inherit', 'inherit'],
-  });
-  if (result.error) {
-    throw new Error(`Failed to run scp: ${(result.error as Error).message}`);
-  }
-  if ((result.status ?? 1) !== 0) {
-    throw new Error(`scp failed copying ${from} -> ${to}`);
-  }
-}
-
-export function shellQuote(value: string): string {
-  return `'${value.replaceAll("'", `'\\''`)}'`;
-}
-
-const REMOTE_RUNTIME_PATH =
-  'PATH="$HOME/.local/bin:$HOME/.bun/bin:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:$PATH"';
-
-/**
- * Non-interactive SSH shells often miss user-installed launchers and Bun.
- * Probe the launcher under the same deterministic PATH used by sync itself.
- */
-export function resolveRemoteSubminerCommand(
-  host: string,
-  preferred: string | null,
-  runRemote: typeof runSsh = runSsh,
-): string {
-  // Trusted defaults stay unquoted so the remote shell expands `~`; a
-  // user-supplied override is shell-quoted to prevent command injection.
-  const candidates: Array<{ value: string; invocation: string }> = preferred
-    ? [{ value: preferred, invocation: shellQuote(preferred) }]
-    : [
-        { value: 'subminer', invocation: 'subminer' },
-        { value: '~/.local/bin/subminer', invocation: '~/.local/bin/subminer' },
-      ];
-  for (const candidate of candidates) {
-    const command = `${REMOTE_RUNTIME_PATH} ${candidate.invocation}`;
-    const probe = runRemote(host, `${command} --help >/dev/null 2>&1`);
-    if (probe.status === 0) {
-      return command;
-    }
-  }
-  throw new Error(
-    preferred
-      ? `Remote command not found on ${host}: ${preferred}`
-      : `subminer not found on ${host} (tried PATH and ~/.local/bin/subminer). Pass --remote-cmd <path>.`,
-  );
-}
+// Re-exported from the shared stats-sync engine so the launcher and the
+// app's --sync-cli mode resolve remotes and shell out identically.
+export {
+  assertSafeSshHost,
+  resolveRemoteSubminerCommand,
+  runScp,
+  runSsh,
+  shellQuote,
+  type RemoteRunResult,
+} from '../../src/core/services/stats-sync/ssh.js';