fix(security): clarify dmScope remediation path with explicit CLI command

# Problem
The security audit and onboarding screens suggested 'Set session.dmScope="..."'
for multi-user DM isolation. This led users to try setting the value in invalid
config paths (e.g., 'channels.imessage.dmScope').

# Changes
- Updated 'src/security/audit.ts' to use 'formatCliCommand' for dmScope remediation.
- Updated 'src/commands/doctor-security.ts' and 'src/commands/onboard-channels.ts'
  to use the explicit 'openclaw config set' command format.

# Validation
- Verified text alignment with 'pnpm tsgo'.
- Confirmed CLI command formatting remains consistent across modified files.

src/security/audit.ts

@@ -599,7 +599,9 @@ async function collectChannelSecurityFindings(params: {
         detail:
           "Multiple DM senders currently share the main session, which can leak context across users.",
         remediation:
-          'Set session.dmScope="per-channel-peer" (or "per-account-channel-peer" for multi-account channels) to isolate DM sessions per sender.',
+          "Run: " +
+          formatCliCommand('openclaw config set session.dmScope "per-channel-peer"') +
+          ' (or "per-account-channel-peer" for multi-account channels) to isolate DM sessions per sender.',
       });
     }
   };