search: redesign TUI results as master-detail list with pinned detail

Replace the dense columnar results table with a two-line list/card layout mirroring the web activity view, and restructure browse mode as a fixed master-detail split so the detail card is always fully visible.

• List rows: type-colored graph node + bold title (commit subject, falling back to commit message then prompt) with right-aligned relative age, plus a dim "type · repo · branch · author" meta line, separated by thin rules.
• Pinned detail pane sized from terminal height (truncated with "enter for more"); list scrolls independently and follows the cursor. Never clipped.
• Type tabs reduced to Checkpoints / Sessions / Commits (no All tab), defaulting to Checkpoints; 10 results per page.
• Status row beneath the list shows a scroll affordance when rows are cut off and "page X/Y · N results"; footer holds only key hints.