fix(Sensitivity): modernize tornado chart and prevent label collisions

[tdody]

Problem

Screenshot feedback showed two issues on the Sensitivity tab's tornado chart:

1. Worst-case value annotations collided with the row labels when a bar extended far to the left (e.g. "Nightly Rate -$2,387" overlapping the "Nightly Rate" row label).
2. Raw red / green / slate colors + pill metric selector were out of sync with the rest of the app.

Changes

Collision fix

• If a downside or upside bar is ≥ 64 px wide, the value text is rendered centered INSIDE the bar with var(--canvas) fill for contrast.
• Narrow bars still render the value outside (end-anchored left of downside, start-anchored right of upside) — but because the bar is close to the baseline in that case, the outside label never reaches into the row-label column.

Design-system integration

• Bar fills use var(--negative) / var(--accent); baseline + baseline-input dashed lines use var(--rule-strong); row labels var(--ink-2); axis labels var(--ink-3).
• Typography: serif 22px chart title, caps "Baseline" label + mono value, mono tabular-nums for every numeric annotation, sans for row labels.
• Container: border border-rule-strong rounded p-6 (dropped the old bg-white / shadow / rounded-xl look).
• Metric selector: replaced the slate pill row with <Segmented> (ink-bg active state, same pattern as the rest of the app).
• Legend: token-colored swatches + caps labels.
• DrillDownChart modernized alongside — accent stroke / points with canvas-ring on the baseline dot, rule-strong dashed zero + baseline-input lines, mono axis labels, border card shell.

Preserved behavior

No data or API changes — getTornado / getLTRTornado calls, the TornadoData / TornadoBar types, and the click-to-drill-down interaction are all unchanged.

Verification

• npm run lint — clean
• npm run build — passes

🤖 Generated with Claude Code