fix: remove the hardcoded 750ms LiveView latency simulator in dev

[chasers]

Problem

The dev root layout called liveSocket.enableLatencySim(750) on every page load:

<%= if Application.get_env(:logflare, :env) == :dev do %>
  <script>
    window.liveSocket.enableLatencySim(750)
  </script>
<% end %>

LiveView then delayed every client message by 750ms:

let latency = this.getLatencySim()
if(!latency){ cb(data) } else { setTimeout(() => cb(data), latency) }

So every click, every phx-change, and every form submit paid 750ms in dev.

Evidence

The server was never slow. Measured on this codebase:

Measurement	Result
change_form_type server render	0.5ms median, 9 KB payload
LiveView mounts (dead render)	6-21ms
Callbacks over 100ms	none

Selecting a backend type renders in 0.5ms, then waits 750ms in the browser.

Side effect this also fixes

enableLatencySim calls enableDebug() first, so dev also logged every LiveView event to the console.

After merging

The value persists in sessionStorage, so removing the script does not clear it. Run this once in the browser console:

liveSocket.disableLatencySim()

Opening a new tab also works.

A developer who wants the simulator can still call liveSocket.enableLatencySim(750) from the console.

🤖 Generated with Claude Code

https://claude.ai/code/session_015XJWSbFFxwiYB25iUAGmXc

[chasers]

Closing for #3986 3986