feat(dashboard): overhaul one-off components page and chart UX

[AndyMBridges]

Summary

This PR rewrites the One-off Components page (formerly "Untracked Components") and adds several UX improvements across the Overview page charts.

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One-off Components page (UntrackedComponents.tsx)

• Renamed "Untracked Components" → "One-off Components" throughout the UI. The page now focuses exclusively on local-oneoff source category entries — platform primitives and third-party packages are excluded from both tables.
• Renamed the two tables to better communicate intent:
  • "Potential MMDS Replacements" → Replace with MMDS today — in-repo one-offs with a direct MMDS equivalent, sorted by migration impact.
  • "Future DS Candidates" → Introduce to MMDS — custom components with no DS equivalent yet, sorted by breadth signal.
• Priority score column added to the "Replace Now" table: instances × confidence weight (exact ×3, strong ×2, partial ×1), visualised as an inline bar.
• Breadth signal column added to the DS Roadmap table: instances × unique teams, surfacing components used widely across the org as stronger roadmap signals.
• Migration vs Overall adoption callout added per project — shows the gap between the tracked migration rate (MMDS ÷ MMDS+deprecated) and the true overall adoption rate (which also counts one-off instances in the denominator), with an explanation of what's driving the difference.
• OneoffTrendChart — new line chart showing replaceable, candidate, and total one-off instance counts over time alongside overall adoption %, with a trend pill showing the weekly change direction.
• SourceCell component replaces the old source-category badge display. Uses a direct tree link when a reliable path is available, falling back to a GitHub code-search link — no more broken 404 links.
• SummaryCard gains colour accent variants (green / purple / blue / amber) to visually differentiate the four stat cards.
• Summary cards updated to show: "Replace Now" count, "Introduce to MMDS" count, teams with one-offs, and the adoption gap in percentage points.
• @unknown owners are filtered out of the team dropdown.

CodeOwnerAdoptionChart.tsx

• Adds a configurable threshold prop (default 90).
• Bars are now colour-coded by adoption %: green ≥ threshold, amber ≥ 70% of threshold, red below — replacing the old blue/orange stacked bars.
• Adds a compliance summary header showing "X / N teams on target" and "Y teams below" as callout cards.
• Teams are sorted by migration % descending (best performing teams first).
• The Recharts Legend is replaced with an inline colour key.

CodeOwnerTrendChart.tsx + CodeOwnerAdoptionTrendChart.tsx

• Both trend charts gain a Team filter dropdown for focusing on a single team's line without losing the overall colour assignment (colours stay stable across filter state).
• Chart height reduces to 300 px in single-team mode (vs 450 px for all teams).

Overview.tsx

• New DeprecatedDeltaSparkline component added below each project's main chart — a compact bar chart showing week-over-week changes in deprecated instances (green = reduction, red = net increase).
• Passes explicit threshold={90} to both CodeOwnerAdoptionChart instances.

Hooks, types & scripts

• New useUntrackedTimeline() hook in useMetricsData.ts — fetches untracked-timeline.json, gracefully handling 404 (returns null).
• New UntrackedProjectTimeline and UntrackedTimeline TypeScript types in metrics.ts.
• New scripts/update-untracked-timeline.js script that builds the timeline JSON consumed by the hook, with a corresponding update-untracked-timeline entry in package.json.

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Test plan

• Open the dashboard locally (cd dashboard && npm run dev) and verify the One-off Components page loads without errors for both Mobile and Extension.
• Confirm the "Replace with MMDS today" table is pre-sorted by Priority score descending.
• Confirm the "Introduce to MMDS" table is pre-sorted by Breadth signal descending.
• Verify the Migration vs Overall adoption callout renders correct percentages and gap.
• Check the Team filter dropdown on both trend charts — selecting a team should isolate that line with stable colouring.
• Check the DeprecatedDeltaSparkline renders on the Overview page for both projects.
• Run yarn update-untracked-timeline to confirm the new script generates untracked-timeline.json correctly, then copy to dashboard/public/metrics/ and verify the OneoffTrendChart renders.
• Build the dashboard (npm run build) and confirm no TypeScript errors.

[socket-security]

No dependency changes detected. Learn more about Socket for GitHub.

👍 No dependency changes detected in pull request

[georgewrmarshall]

Really nice 🔥 Just need to investigate and address socket security issue