fix(tui): dag inspector frame alignment, padding, and wave grouping

[LeXwDeX]

Summary

Aligns the /dag inspector with the diff-viewer's native TUI design language, fixing three visual defects:

1. Floating ┬/├/┴ separator glyphs: the right pane never drew a left vertical border, so the horizontal separators' edge characters hung floating without a line to join. Every content block in the right pane (status row, node list, detail pane) now carries border={["left"]}, forming one continuous frame — same construction as the diff-viewer's patch pane.
2. Misaligned bottom rule: the workflow list's bottom border ended at column 32 with nothing continuing. A closing Separator start="edge-in" (┴) at the bottom of the right pane now closes the frame flush across the full width.
3. No padding / no wave zoning: workflow rows, node rows, header, and footer gain consistent paddingLeft/paddingRight; wave headers switch to an accent-colored label (matching which-key's section-header idiom) with a blank spacer line between waves; node names use text while active and drop to textMuted only once settled.

computeNodeRowIndex counts the new inter-wave spacer rows so scroll-into-view stays correct; its unit test updated accordingly.

Test plan

• tsgo --noEmit clean in packages/tui
• 41/41 DAG inspector + utils tests pass (bun test test/feature-plugins/dag-inspector*.test.* from packages/tui), including the fixed-footer and blank-outer-row layout regressions
• Frame verified via test harness render: continuous ┬/├/┴ frame, full-width closing rule, spaced wave blocks