feat: add frequency-based route color visualization

[Gaudv]

Description
Map appearance: improve frequency-based arc styling (color + thickness) with percentile scaling.

Issues
Raw frequency values were dominated by extreme routes, collapsing many routes into near-identical visuals.
(ex, if one route is flown 100 times, a route flown 20 times will have no visual difference with a route flown 1 time)

Changes

• patch: arc thickness by frequency uses percentile-based scaling instead of absolute value.
• add: arc color by frequency.

---

Summary by cubic

Improved route frequency visualization: arc thickness now uses percentile scaling and arcs can color by frequency, making busy routes stand out without flattening others. Adds a simple control in Map Appearance and persists the choice.

• New Features
  • Arc thickness uses percentile ranks (per-route, undirected keys) instead of raw counts.
  • New arc color mode: "By frequency" blends base colors toward red as frequency increases; default remains unchanged.
  • Map Appearance → Arcs → Color with "Default" and "By frequency".
  • Preferences: added arcColor to MapPreferences; sanitized, persisted, and resettable.
  • Internals: deck.gl update triggers now include arcColor and per-route percentiles for color and width recalculation.

^{Written for commit ba1aa6c. Summary will update on new commits.}

Note

Add frequency-based route color visualization to the flights map

• Adds a new byFrequency arc color mode that blends each route's source/target color toward a high-frequency red based on its percentile rank across all routes.
• Adds ArcColorMode type, arcColor preference (defaulting to 'default'), and wires it through localStorage persistence, sanitization, and reset in map-preferences.svelte.ts.
• Exposes a 'Routes → Color' selector in MapAppearanceControl.svelte with 'Default' and 'By frequency' options; also moves the reset action to the panel header.
• Behavioral Change: when arc width is set to byFrequency, widths are now driven by a normalized 0–1 percentile scale instead of absolute frequency counts, so visual thickness is relative rather than absolute.

^{Macroscope summarized 920799d.}

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/lib/components/map/AirportsArcsLayer.svelte">

<violation number="1" location="src/lib/components/map/AirportsArcsLayer.svelte:274">
P2: by-frequency arc thickness can evaluate to 0 for the lowest-frequency route, making that route invisible in the main ArcLayer.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud