fix(daemon): replace bootout with kickstart -k for launchd restarts on macOS

On macOS, launchctl bootout permanently unloads the LaunchAgent plist.
Even with KeepAlive: true, launchd cannot respawn a service whose plist
has been removed from its registry. This left users with a dead gateway
requiring manual 'openclaw gateway install' to recover.

Affected trigger paths:
- openclaw gateway restart from an agent session (#43311)
- SIGTERM on config reload (#43406)
- Gateway self-restart via SIGTERM (#43035)
- Hot reload on channel config change (#43049)

Switch restartLaunchAgent() to launchctl kickstart -k, which force-kills
and restarts the service without unloading the plist. When the restart
originates from inside the launchd-managed process tree, delegate to a
new detached handoff helper (launchd-restart-handoff.ts) to avoid the
caller being killed mid-command. Self-restart paths in process-respawn.ts
now schedule the detached start-after-exit handoff before exiting instead
of relying on exit/KeepAlive timing.

Fixes #43311, #43406, #43035, #43049

CHANGELOG.md

@@ -81,6 +81,7 @@ Docs: https://docs.openclaw.ai
 - Telegram/outbound HTML sends: chunk long HTML-mode messages, preserve plain-text fallback and silent-delivery params across retries, and cut over to plain text when HTML chunk planning cannot safely preserve the full message. (#42240) thanks @obviyus.
 - Agents/embedded overload logs: include the failing model and provider in error-path console output, with lifecycle regression coverage for the rendered and sanitized `consoleMessage`. (#41236) thanks @jiarung.
 - Agents/failover: treat Gemini `MALFORMED_RESPONSE` stop reasons as retryable timeouts so preview-model enum drift falls back cleanly instead of crashing the run, without also reclassifying malformed function-call errors. (#42292) Thanks @jnMetaCode.
+- Gateway/macOS launchd restarts: keep the LaunchAgent registered during explicit restarts, hand off self-restarts through a detached launchd helper, and recover config/hot reload restart paths without unloading the service. Fixes #43311, #43406, #43035, and #43049.
 - Discord/Telegram outbound runtime config: thread runtime-resolved config through Discord and Telegram send paths so SecretRef-based credentials stay resolved during message delivery. (#42352) Thanks @joshavant.
 - Secrets/SecretRef: reject exec SecretRef traversal ids across schema, runtime, and gateway. (#42370) Thanks @joshavant.
 - Telegram/docs: clarify that `channels.telegram.groups` allowlists chats while `groupAllowFrom` allowlists users inside those chats, and point invalid negative chat IDs at the right config key. (#42451) Thanks @altaywtf.