Auto-show web widgets on update

[edwin-zvs]

Summary

• auto-open the web widget popover when a live widget update arrives for the active session
• add a 15s temporary visibility deadline that auto-hides the popover and extends while hovered or focused
• preserve background-session updates so switching to that session before the deadline still reveals the widget
• add web smoke coverage for active-session autoshow, deadline close, and background-session reveal-on-switch

Validation

• node script parse check for the inline web UI script
• cargo build
• cargo test -p agentd-e2e web_client_loads_and_websocket_connects -- --nocapture
• git diff --check

Built debug binaries

• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agent
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-mcp
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-adapter-antigravity
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-adapter-claude
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-adapter-codex
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-adapter-shell
• /Users/moon/agentd/.claude/worktrees/webui-widget-autoshow/target/debug/agentd-adapter-zarvis

Relevant binary: this PR changes the daemon web UI assets, so run agentd to test the web client behavior.