Fix issues with Fleet desktop periodically not appearing on macOS hosts

[ghernandez345]

Goal

User story
As a user of a fleet desktop,
I want to ensure that Fleet desktop is available on my macOS host
so that I can always have access to my host details on Fleet.

Key result

Ensure a more stable fleet desktop experience where Fleet desktop is always available on a macOS host.

There have been issues where Fleet desktop periodically "disappears" on macOS hosts, so users cannot interact with Fleet desktop and cannot access their host information on Fleet. The cause is unclear, but it is thought that Fleet desktop, currently running as a daemon, maybe the issue and changing it to a launch agent instead may help. We are not certain if this will fix the issues though.

We could also surface information in Fleet or on the host that the host's Fleet desktop is not running and that action needs to be taken (e.g. a restart of the host). If we decide to go this route, some product ideation will be required.

Here are the current related bugs:

• Fleet desktop not launching after macOS OS update to 15.2 #25689
• [WAITING] Fleet Desktop missing on MDM enrolled macOS host after reset all settings #19499

Original requests

None

Context

• Product designer: _________________________

Changes

Product

• UI changes: TODO
• CLI (fleetctl) usage changes: TODO
• YAML changes: TODO
• REST API changes: TODO
• Fleet's agent (fleetd) changes: TODO
• Activity changes: TODO
• Permissions changes: TODO
• Changes to paid features or tiers: TODO
• Transparency changes: TODO
• First draft of test plan added
• Other reference documentation changes: TODO
• Once shipped, requester has been notified
• Once shipped, dogfooding issue has been filed

Engineering

• Test plan is finalized
• Feature guide changes: TODO
• Database schema migrations: TODO
• Load testing: TODO

ℹ️  Please read this issue carefully and understand it. Pay special attention to UI wireframes, especially "dev notes".

QA

Risk assessment

• Requires load testing: TODO
• Risk level: Low / High TODO
• Risk description: TODO

Test plan

1. Step 1
2. Step 2
3. Step 3

Testing notes

Confirmation

1. Engineer: Added comment to user story confirming successful completion of test plan.
2. QA: Added comment to user story confirming successful completion of test plan.

[georgekarrv]

Adding #19172