Menu card: ember particles drifting while the menu is open

[tangentlin]

Motivation

Reinforce the "burn" identity on the one card users actually stop to look at: while the tray menu is open, a few faint ember particles drifting upward from the bar chart would add ambient life without competing with the numbers.

Proposal

Start a short-lived particle animation loop when the menu opens (a handful of small glowing dots rising and fading from the top of the drawBars region), stopped when the menu closes.

Feasibility notes

• Needs a hook into the menu's open/close lifecycle (Electron Menu emits menu-will-show/menu-will-close events) to start/stop a RAF loop in the hidden card-renderer window, then push updated PNG frames back through MenuCardRenderer while open.
• This is the most speculative of the menu-card ideas effort-wise — today's architecture renders one PNG per data change, not a continuous stream to a live menu item; worth a small spike to confirm Electron's menu-item icon can be swapped smoothly enough (frame rate, flicker) before committing.

Acceptance criteria

• Particle animation runs only while the tray menu is open; stops cleanly on close (no orphaned timers/RAF loops).
• Subtle enough not to obscure the stat values or bar chart.
• Spike/prototype confirms acceptable frame rate and no visible flicker before full implementation.