Richer, more interactive chart data exploration (Token Terminal–style)

**Request:** Make the Explorer charts a richer, more interactive data-exploration surface — closer to what Token Terminal offers — so delegators and orchestrators can dig into the metrics rather than just glance at them.

**Rationale:** As daily data accumulates, the small fixed-window panels are increasingly hard to read and analyze. Delegators have asked for charts that are interactive with better handling of the visible data frame (date range), and have pointed to Token Terminal as the reference experience. The original ask here was simply to expand/separate panels; this issue broadens it to cover the full interactivity gap.

**What exists today**
- Grouping toggles only: D/W on bar charts, Y/All on line charts
- Hover tooltip with exact value + date
- No custom date range, zoom/pan, brush, expand-to-fullscreen, or data export

**Proposed scope**
- [ ] Expand a panel to a larger size / dedicated full-screen or per-metric page (original #318 ask)
- [ ] Custom / draggable date-range selection (the "data frame" handling delegators asked for) — e.g. brush selector or range presets (7D / 30D / 90D / YTD / 1Y / All)
- [ ] Zoom & pan within the selected range
- [ ] Richer tooltips/crosshair (value, % change vs range start, exact timestamp)
- [ ] Export the visible data frame (CSV / PNG)
- [ ] (Stretch) Overlay/compare multiple metrics on one chart

**Notes**
- Initial interactivity work is in progress on \`feat/interactive-charts\` (custom axis ticks, improved tooltips, time-scale x-axis). This issue tracks the broader Token Terminal–style exploration on top of that.
- Reported by delegator feedback; happy to take PRs against this.

Start by reviewing the existing Explorer chart panels and the feat/interactive-charts branch, which already covers axis ticks, tooltips, and a time-scale x-axis. Define a focused subset of the proposed interactions, then verify that the selected range, navigation, tooltip details, and any export behavior work as specified.

Written by the indexing model from the issue text.