fix(contacts/map): align line colors with sidebar legend

The polylines were sourcing from --band-* CSS vars (a separate, theme-aware
design palette) while the legend swatches rendered from the Elixir @band_colors
map, so the two diverged for every band — e.g. 10 GHz showed lime on the map
and emerald in the legend. Emit `data-band-color` on each band checkbox and
have the JS hook read from there, making the legend the single source of truth.
Drops the now-redundant theme observer / restyleLines plumbing.

assets/js/contacts_map_hook.ts

@@ -40,7 +40,6 @@ interface ContactsMapHook extends ViewHook {
   map: L.Map
   delegatedChange: (e: Event) => void
   delegatedClick: (e: Event) => void
-  themeObserver: MutationObserver | null
   initMap(this: ContactsMapHook): void
   buildLines(this: ContactsMapHook): void
   syncBandLayers(this: ContactsMapHook): void
@@ -49,7 +48,6 @@ interface ContactsMapHook extends ViewHook {
   updateCount(this: ContactsMapHook, count: number): void
   wireControls(this: ContactsMapHook): void
   unwireControls(this: ContactsMapHook): void
-  restyleLines(this: ContactsMapHook): void
 }
 
 function inDateRange(tsDate: string, startDate: string, endDate: string): boolean {
@@ -60,48 +58,26 @@ function inDateRange(tsDate: string, startDate: string, endDate: string): boolea
   return true
 }
 
-// Amateur-band palette. Nine of these map to the design system's --band-*
-// CSS vars (defined in assets/css/app.css); the higher mm-wave bands above
-// 47 GHz fall back to hard-coded hues since the design set only spans up
-// to 6mm. CSS vars are resolved once per page via getComputedStyle because
-// Leaflet writes the color onto the SVG `stroke` attribute, which does not
-// evaluate `var()` references.
-const BAND_VAR: Record<number, string> = {
-  1296:  "--band-23cm",
-  2304:  "--band-13cm",
-  3400:  "--band-9cm",
-  5760:  "--band-6cm",
-  10000: "--band-3cm",
-  24000: "--band-1-25cm",
-  47000: "--band-6mm",
-}
-
-const BAND_FALLBACK: Record<number, string> = {
-  68000:  "#dc2626",
-  75000:  "#c026d3",
-  122000: "#db2777",
-  134000: "#e11d48",
-  241000: "#b91c1c",
-}
-
+// Band colors are sourced from the legend swatches in the sidebar — each
+// band checkbox carries `data-band-color` set server-side from
+// `Microwaveprop.ContactMapLive`'s @band_colors map. Reading from the DOM
+// keeps the legend the single source of truth: change the Elixir map and
+// both the swatch and the polyline update in lockstep.
 let BAND_COLORS: Record<number, string> | null = null
 
 function resolveBandColors(): Record<number, string> {
   if (BAND_COLORS) return BAND_COLORS
-  const styles = getComputedStyle(document.documentElement)
-  const resolved: Record<number, string> = { ...BAND_FALLBACK }
-  for (const [band, cssVar] of Object.entries(BAND_VAR)) {
-    const value = styles.getPropertyValue(cssVar).trim()
-    if (value) resolved[Number(band)] = value
+  const resolved: Record<number, string> = {}
+  const inputs = document.querySelectorAll<HTMLInputElement>("input[data-band][data-band-color]")
+  for (const inp of inputs) {
+    const band = parseInt(inp.dataset.band || "", 10)
+    const color = inp.dataset.bandColor
+    if (Number.isFinite(band) && color) resolved[band] = color
   }
   BAND_COLORS = resolved
   return resolved
 }
 
-function invalidateBandColors(): void {
-  BAND_COLORS = null
-}
-
 function bandLabel(mhz: number): string {
   if (mhz >= 1000) {
     const ghz = mhz / 1000
@@ -125,7 +101,6 @@ export const ContactsMap = {
     this.bandGroups = new Map()
     this.lines = []
     this.dotLayer = L.layerGroup()
-    this.themeObserver = null
 
     // Callsign filter still roundtrips through LiveView (debounced) — it's
     // cross-cutting and fires rarely. Band toggles are purely client-side.
@@ -144,18 +119,6 @@ export const ContactsMap = {
 
     this.wireControls()
 
-    // Re-color polylines when the theme toggles. Leaflet writes `stroke` as
-    // an SVG attribute (which does not resolve CSS vars), so we re-read the
-    // resolved --band-* values and call setStyle on each line.
-    this.themeObserver = new MutationObserver(() => {
-      invalidateBandColors()
-      this.restyleLines()
-    })
-    this.themeObserver.observe(document.documentElement, {
-      attributes: true,
-      attributeFilter: ["data-theme"]
-    })
-
     requestAnimationFrame(() => this.initMap())
 
     fetch(fetchUrl)
@@ -174,16 +137,6 @@ export const ContactsMap = {
 
   destroyed(this: ContactsMapHook) {
     this.unwireControls()
-    if (this.themeObserver) {
-      this.themeObserver.disconnect()
-      this.themeObserver = null
-    }
-  },
-
-  restyleLines(this: ContactsMapHook) {
-    for (const entry of this.lines) {
-      entry.line.setStyle({ color: bandColor(entry.band) })
-    }
   },
 
   wireControls(this: ContactsMapHook) {

lib/microwaveprop_web/live/contact_map_live.ex

@@ -202,6 +202,7 @@ defmodule MicrowavepropWeb.ContactMapLive do
                       type="checkbox"
                       checked
                       data-band={band}
+                      data-band-color={band_color(band)}
                       style={"accent-color:#{band_color(band)}"}
                     />
                     <span
@@ -325,6 +326,7 @@ defmodule MicrowavepropWeb.ContactMapLive do
                   type="checkbox"
                   checked
                   data-band={band}
+                  data-band-color={band_color(band)}
                   style={"accent-color:#{band_color(band)}"}
                 />
                 <span