fix(tui): keep pane ordinals above playbooks

[edwin-zvs]

What

Paint split-pane ordinal badges in the final pane-overlay pass, after rolled-down Playbooks and transition overlays. This keeps each badge visible at its pane corner regardless of which pane surface is open.

Adds a regression test covering a rolled-down Playbook in a split layout.

Why

PR #1257 made pane ordinals both locators and addresses, but the Playbook compositor ran after the leaf-local badge paint and covered the active pane badge. The accepted spec already requires badges to be painted after pane content and transient overlays.

Testing

• cargo build
• cargo test -p construct-cli ordinal_badge -- --nocapture (5 passed)
• cargo test -p construct-cli -- --skip color::tests::truecolor_backend_still_emits_rgb (1,411 unit tests + reconnect integration test passed)
• Full unfiltered CLI suite has the existing color::tests::truecolor_backend_still_emits_rgb failure; reproduced unchanged on main.

This PR only touches crates/cli → relevant binary is construct.

[edwin-zvs]

Before — badge covered by rolled-down Playbook:

After — badge remains visible above the rolled-down Playbook: