Fix TUI freeze on row-only PTY growth

[edwin-zvs]

Summary

• avoid full PTY history replay when the main pane only grows in rows
• apply the cheap row-only resize path to both cached PTY replay and tool-block-aware replay
• add regressions for plain PTY history and Zarvis/tool-block history

Verification

• cargo test -p agentd-cli rows_grow
• cargo build --workspace --all-targets --locked
• cargo test --workspace --locked -- --skip pty_render::tests::codex_initial_render_after_restart_is_bounded --skip pty_render::tests::many_pinned_sessions_resize_within_budget --skip pty_render::tests::pseudo_terminal_render_is_fast_per_frame --skip pty_render::tests::codex_resize_bound_is_reasonable
• git diff --check

Relevant code is in crates/cli, so the binary to try is target/debug/agent.