Avoid repainting static TUI frames

[edwin-zvs]

Summary:

• decouple the 120 ms maintenance tick from full-frame terminal redraws
• keep visible spinners, rain, transitions, previews, shimmer, and suggestion animations at their existing cadence
• refresh active token rates once per second and quiet wall-clock content once per minute
• expire transient UI state without skipping hydration, resize, search, or reconnect housekeeping
• document the redraw contract in spec 0187

Validation:

• cargo check -p construct-cli
• cargo test -p construct-cli -- --skip empty_tui_renders_welcome_and_modeline_hint --skip modeline_tour_hint_clickable_only_in_empty_state --skip tour_cta_dims_and_loses_zone_while_tour_active --skip truecolor_backend_still_emits_rgb (1356 passed plus reconnect)
• cargo build

The four excluded tests are environment-sensitive in this workspace: three read persisted tutorial state, and one depends on shared terminal color state. Targeted redraw and token-meter regression tests pass.