cross-cutting: zIndex config (default 2147482647 — max − 1000)

[productdevbook]

Every provider fights for top of the stacking context. Apps want control.

Evidence

• `[CW-2556] If chatwoot fails to load, nothing else is clickable on the page chatwoot/chatwoot#7974` [CW-2556] If chatwoot fails to load, nothing else is clickable on the page chatwoot/chatwoot#7974
• `Allow changing the z-index of the Chatwoot widget chatwoot/chatwoot#8957` / `#2180`
• Olark docs: default 999999
• Beacon: 1050

Tasks

• `load({ zIndex })` applies via CSS variable injection (`--ahize-z-index`) + per-provider setting
• Default `2147482647` (max − 1000) so user modals can sit on top
• Document per-provider enforcement depth (iframe z-index vs host container)

[productdevbook]

Implemented in this commit