[rabden]

Problem

OpenCode model discovery used a fixed 10-second timeout even though the ACP runtime handshake allows 120 seconds. On plugin-heavy installations, OpenCode can take tens of seconds or minutes to initialize its plugin/MCP graph, causing the model picker to cache a timeout or static fallback rather than the actual catalog.

Fix

• Give OpenCode one shared, configurable five-minute startup budget for both the ACP handshake and model discovery (ZERON_OPENCODE_STARTUP_TIMEOUT_SECS).
• Surface OpenCode discovery failures instead of silently substituting static catalog rows.
• Serialize concurrent discovery probes so opening/rendering the picker cannot spawn duplicate OpenCode processes.
• Retry transient OpenCode catalog failures twice in the picker, preserving already loaded rows while refreshing.
• Add a thin floating model-list scrollbar which appears only while its scrollable list is hovered; it supports track clicks and captured thumb dragging without layout reflow.

Validation

• cargo test -p zeron-harness
• cargo check -p zeron-ui
• cargo test -p zeron-ui --lib

[rabden]

@wingleeio without this opencode models dont even load.