#32179 cmux NEXT: the host pressure indicator ships on

Leo asked for cmux NEXT itself to warn on CPU and RAM pressure:

i mean cmux next itself should be more cpu and ram aware... with stat or whatenot. maybe even acpmux itself.. just warn for now instead of prenveting stuff

The indicator, popover and monitor already landed (#24298, #24507, #24518), but hostPressure.enabled shipped off as a Debug toggle. A feature Leo asked for ships on by default, so this flips that one default to true. Release and RC never activate the tunable store, so they now read the new default and show the indicator too.

• On: the top-row gauge after the toolbar band. A normal host shows nothing. Warning and critical show a still glyph with the existing popover: the load against its limit, acpmux's reasons and the busiest sessions. It only warns and prevents nothing.
• Unchanged: the critical banner (hostPressure.banner) stays off.
• Cost: one app-wide 15 s DispatchSourceTimer (2 s leeway), so 4 reads a minute while at least one window can be seen.
• Stop condition: it stops when every window is hidden, minimized, occluded or closed, or when the toggle goes off. #24507 has the measured cost: the timer's wakeups are below run-to-run noise.
• Tests: theToggleShipsOnAndOffNeverMakesTheService now pins the default as on and still checks that off makes no service. The banner test sets the toggle off explicitly before it checks the off → on edge.
• Tour: the launch step's title now says the indicator ships on.

Small change: one default, its doc comment and help text, and two test setups.

Leo-ask: ask-8827679cab

Agent session: agent session

🤖 Generated with Claude Code

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Summary by cubic

Ships the host pressure indicator in cmux NEXT on by default: hostPressure.enabled now defaults to true instead of shipping off behind a Debug toggle, so Release and RC builds also show it.

• On: a still gauge after the toolbar band appears when the Mac is busy or overloaded, with a popover showing the load against its limit, acpmux's reasons, and the busiest sessions. Warning only — nothing is prevented.
• The critical banner (hostPressure.banner) stays off.
• Cost: one 15 s app-wide DispatchSourceTimer (2 s leeway) that runs only while at least one window is visible; measured wakeups are below run-to-run noise.
• Tests now pin the default to on, and the banner test sets the toggle off explicitly before checking the off → on edge.