[BUG] Logo charge-hum audio leaks after mouseout: coreaudiod pinned at 480% CPU, painful continuous noise on output device #24668

Summary

The TUI logo "burst" feature added in #22098 leaves audio playback in a broken
state after mouse interaction ends. The synthesized charge/burst tones do not
stop cleanly — they degrade into continuous loud scratching, buzzing, and
hissing on the system audio output device. coreaudiod simultaneously pins a
CPU core at near-100% (observed: 480.5% CPU on an M4 Max, i.e. ~5 cores
saturated). The noise persists indefinitely until OpenCode is killed or the
audio output device is power-cycled.

On headphones the artifact is severe enough to be physically painful —
closer to a stuck oscillator with a runaway envelope than a normal "click" of
an incomplete sample. This is consistent with a generated-tone code path (per
the PR's own commit message: "Give the logo pulse a generated charge hum and
burst sound", 7d853f3)
where the oscillator/gain node is not torn down when the mouse leaves the logo
hit region.

Reproduction

1. Launch opencode (v1.14.28) in a terminal that supports mouse reporting.
2. Move the mouse cursor over the TUI logo. Hold briefly, then move away.
3. Observe: the charge/burst sounds play, then transition into a continuous
   loud noise on the default output device.
4. Run top -o cpu or Activity Monitor — coreaudiod is at several hundred
   percent CPU.
5. Noise does not stop on its own. Killing the `opencode` process stops it.

Environment

Suspected cause

PR #22098 ships generated audio (oscillator + gain envelopes) rather than
sample playback. A likely failure mode:

• A `mouseenter` / `mousedown` event starts the charge oscillator.
• The corresponding `mouseleave` / `mouseup` / cancellation path does not
  always run (event missed, debounce race, or the burst-release branch
  short-circuits the cleanup), so the oscillator keeps emitting and its gain
  node is never ramped to zero or stopped.
• The runaway tone, combined with whatever the audio backend is doing on the
  Zig/native side, drives `coreaudiod` into a hot loop.

The kitty terminal aggressively reports mouse motion events, which may make
the mismatched-event scenario much more likely to fire than in terminals that
report only clicks.

Severity

This is not a cosmetic issue. Headphone users (the population most likely to
be running a CLI dev tool quietly) get a sudden, loud, sustained,
non-attenuating noise directly into their ears with no in-app way to stop it.
That is a real risk of hearing discomfort or harm. The only mitigations
currently available are:

• Kill OpenCode.
• Yank the headphone/USB cable.
• Mute at the OS level before opening OpenCode.

There is no documented setting to disable the logo audio. Issue #22528 has
been open since April 15 asking for a toggle and is not yet resolved (PR
#23086 referenced but not shipped at 1.14.28).

Asks

1. Immediate: ship a way to disable logo sound effects (preferably
   off by default, given the active complaints on feat: add interactive burst to the TUI logo #22098 and How to turn off sound effects and animations in 1.4.4 #22528).
2. Fix: audit the oscillator/gain lifecycle in the logo burst code so
   that any path out of the charge state (mouseleave, focus loss, terminal
   resize, app backgrounded, exit) deterministically stops every audio node
   it created. Add a watchdog that hard-stops audio after N ms with no
   active interaction.
3. Forward-looking, said respectfully: please weigh the cost/benefit
   before shipping decorative TUI features that produce audio. A logo
   easter-egg is fun. A logo easter-egg that, when buggy, plays painfully
   loud noise into a developer's headphones with no off switch is not a
   feature — it is a liability. Audio output from a developer tool should
   default to off, be opt-in, and have a kill switch documented in the
   release notes.

Happy to provide a screen recording with audio if that would help.