feat: filter trails by activity + backfill trail activities

[fatherlinux]

Summary

Selecting an activity like Biking in the map legend left hiking-only trails (Seneca, Sand Run Parkway, Ledges, etc.) on the map — the Trails layer was only gated by its on/off toggle and never honored activity selection. Compounding it, 144 of 179 trails had no primary_activities at all, and a dozen footpaths were mis-tagged as bikeable.

Code (frontend)

• iconUtils.js: isActivityFilterActive() + trailPassesActivityFilter(). Untagged trails always render (a missing tag never silently hides a trail); when the legend is narrowed to specific activity types, a tagged trail shows only if its activities match. Plain "Trails" browsing (all/none activities selected) is unchanged.
• Map.jsx: trail rendering now gated on showTrails && trailPassesActivityFilter(...) in both MapBoundsTracker and the render path.

Data (migration 075, idempotent)

• 144 untagged trails -> Hiking.
• Dropped Biking from 11 mis-tagged footpaths (kept their other tags).
• Bikeable allowlist keeps Hiking+Biking: Towpath, Bike & Hike, Freedom Trail, Gateway (West Creek paved connector), Cleveland Foundation Centennial, Cleveland Lakefront Bikeway, Solon to Chagrin Falls, Portage Hike & Bike, Mud Brook Greenway, Advanced drop section (MTB).
• Result: trails tagged Biking 21 -> 10, untagged 144 -> 0.

Test plan

• Verified locally: None -> Biking -> Trails shows exactly 10 bikeable trails; Seneca / Parkway Jogging / Ledges correctly hidden.
• None -> Trails alone still shows all trails (filter only engages for a specific activity).
• Migration re-runs as UPDATE 0 / UPDATE 0 (idempotent).
• gourmand --full . passes (0 violations).

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces a database migration to backfill and correct trail activities, and updates the frontend map rendering to filter trails based on the active activity selection. The review feedback highlights a performance bottleneck in isActivityFilterActive, which is called repeatedly for every trail feature during rendering. Caching the filter status and adding defensive checks for visibleTypes and feature are recommended to optimize performance and prevent potential runtime errors.

[gemini-code-assist]

Performance Bottleneck & Defensive Programming

1. Performance Bottleneck: isActivityFilterActive is called inside trailPassesActivityFilter for every single trail feature (e.g., 179 trails) during map rendering and bounds tracking. Since isActivityFilterActive only depends on visibleTypes and iconConfig (which are constant for a given render pass), this results in redundant loops over iconConfig hundreds of times per render. We can optimize this by caching the last computed result using reference equality checks on visibleTypes and iconConfig.
2. Defensive Programming: Added defensive checks to ensure visibleTypes is a valid Set (or has a has method) and feature is non-null before accessing their properties.

let lastVisibleTypes = null;
let lastIconConfig = null;
let lastResult = false;

export function isActivityFilterActive(visibleTypes, iconConfig) {
  if (visibleTypes === lastVisibleTypes && iconConfig === lastIconConfig) {
    return lastResult;
  }
  lastVisibleTypes = visibleTypes;
  lastIconConfig = iconConfig;

  if (!iconConfig || iconConfig.length === 0) {
    lastResult = false;
    return false;
  }
  if (!visibleTypes || typeof visibleTypes.has !== 'function') {
    lastResult = false;
    return false;
  }

  let activityTypes = 0, selected = 0;
  for (const icon of iconConfig) {
    if (icon.enabled === false || !icon.activity_fallbacks) continue;
    activityTypes++;
    if (visibleTypes.has(icon.name)) selected++;
  }
  lastResult = selected > 0 && selected < activityTypes;
  return lastResult;
}

/**
 * Whether a trail (linear feature) should render given the current activity
 * narrowing. Untagged trails always show, so a missing tag never silently hides a
 * trail. (Selecting "Biking" hides hiking-only trails.)
 */
export function trailPassesActivityFilter(feature, visibleTypes, iconConfig) {
  if (!feature) return true;
  if (!isActivityFilterActive(visibleTypes, iconConfig)) return true;
  if (!(feature.primary_activities || '').trim()) return true;
  return poiMatchesActivityForTypes(feature, visibleTypes, iconConfig);
}

[fatherlinux]

Superseded — reworking on current master (production already shipped a different trail filter in #453; this redo applies the stricter hide-non-matching behavior + data backfill on top).