Overview

Three related UX improvements to /ash that work together to make the TUI feel like a real monitoring tool rather than a read-only display.

1. Reassign zoom keys: [/] instead of ←/→

Current: ←/→ cycle zoom levels. This is the wrong mental model — left/right arrows should mean "move in time", not "change scale".

Change:

• [ = zoom out (wider time window)
• ] = zoom in (narrower time window)
• ←/→ = pan/scrub through history (see below)

Footer hint updates accordingly: [/]:zoom ←→:pan

In Live mode, pressing ← auto-switches to History mode anchored at "now" and starts panning backward.

2. History pan/scrub with ←/→ + vertical cursor line

When in History mode (or after pressing ← from Live):

• ←/→ shifts the time window backward/forward by one bucket width
• A vertical cursor line │ is drawn at the "selected" column in the timeline
• A floating infobox appears (bottom-right of timeline or replacing the drill-down hint area) showing the exact breakdown for that moment:
  • Timestamp of the bucket
  • AAS value
  • Top wait types with counts and % share
  • Color-coded to match bar colors

This is the keyboard equivalent of a Grafana hover tooltip — instant drill-in to any historical moment without leaving the timeline view.

State additions:

• cursor_col: Option<usize> in AshState — None = no cursor, Some(col) = column index from right
• pan_offset: i64 — how many buckets we've shifted from "now"

3. Context-sensitive upper timeline on drill-down

Current: Drill into Lock in the bottom pane → top timeline still shows all wait types stacked. The two halves are disconnected.

Proposed: The timeline adapts to the current drill level:

This makes the top and bottom halves a coherent unit — as you drill in, both panes zoom into the same slice of data.

Color handling: At WaitEvent level, use a deterministic hash of the event name to pick from the existing color palette. At QueryId level, same approach with query_id.

Implementation order

1. Zoom key reassignment — purely a state.rs keybinding change, no renderer touch. 1-2 hours.
2. History pan + cursor line — adds cursor_col/pan_offset to AshState, one renderer pass to draw │ and infobox. ~half day.
3. Context-sensitive timeline — touches renderer.rs bar-building logic to filter/recolor by drill level. ~1 day.

All three are independent of any other open PR.

Acceptance criteria

• [/] change zoom level; ←/→ pan the time window
• Pressing ← in Live mode transitions to History mode automatically
• Vertical cursor line visible when panning; infobox shows bucket stats
• At WaitEvent drill level, timeline bars show individual events within that type
• At QueryId drill level, timeline bars show individual queries
• Footer hints stay accurate at each level
• All existing drill-down, zoom, legend, and exit behavior unchanged