fix(launchd): use unconditional KeepAlive so gateway restarts after clean exit #37388

[kyssta-exe]

Summary

The launchd plist shipped with KeepAlive.SuccessfulExit=false, which meant launchd only restarted the gateway on non-zero exit. When gateway run --replace triggered a clean exit (code 0), launchd did not relaunch it, leaving the gateway down indefinitely until manually restarted.

Fix

Changed KeepAlive from:

<key>KeepAlive</key>
<dict>
    <key>SuccessfulExit</key>
    <false/>
</dict>

To:

<key>KeepAlive</key>
<true/>

This ensures the gateway always restarts regardless of exit code, which is the correct behavior for a long-lived service managed by launchd.

Testing

• All 13 existing launchd-related tests pass
• Verified the generated plist output contains unconditional <true/> KeepAlive
• No functional changes to gateway restart logic on other platforms

Fixes #37388

[alt-glitch]

Duplicate of #37411 — both make the launchd plist KeepAlive unconditional (<true/>) so the gateway restarts after a clean gateway run --replace exit. Same root cause as #9659 / #37388, and same fix proposed in #9689 / #14001. Consolidating on one PR would help.

[teknium1]

Fixed via PR #39000 (#39000), merged to main. Same fix as yours — the salvaged implementation (#38796) shipped with the launchd test. Credited as a duplicate contributor. Thanks!