[edwin-zvs]

Summary

• Open Program as a roll-down surface covering about two thirds of the session pane, leaving the bottom third of the terminal visible.
• Add a draggable Program bottom border to resize how much of the session pane Program covers.
• Let clicks in the exposed terminal fall through and give terminal keyboard focus without hiding or rolling up Program.
• Dim the Program border while the exposed terminal has focus as a visual affordance.
• Preserve the user-adjusted coverage across hide/show for that session.

Tests

• cargo test -p agentd-cli program_ -- --nocapture
• cargo build

Binary

This PR only touches crates/cli; relevant debug binary:

• /Users/moon/agentd/.claude/worktrees/program-roll-down-resizable-v2/target/debug/construct