feat: distance from me on channel detail, proximity sort, operator marker on maps

[pskillen]

Problem

When out and about, an operator may have their codeplug on a phone and want to know how far they are from a repeater or other geolocated channel — and see it on a map. Today:

• Channel detail shows coordinates, locator, and an embedded map, but no distance from the operator.
• Channel list sorts alphabetically only; no proximity sort.
• Maps (CodeplugMap on channel detail, channel list, zone detail) plot channels/zones but not the operator's position.

#59 shipped UseMyLocationButton for seeding coordinates on edit/converter, but there is no session operator position reused across browse views for distance and map context.

Intended outcome

Add operator-position awareness for field use — distance display, proximity sort, and "you are here" on maps.

Operator position (session)

• Introduce a session-scoped operator position (lat/lon + optional accuracy), obtained via existing useGeolocation / UseMyLocationButton — not persisted to localStorage or codeplug.
• Provide a shared hook or context, e.g. useOperatorPosition() — set on explicit user action; clear on tab close or manual "Clear my location".
• Surfaces to obtain position:
  • Use my location on channel detail (and optionally channel list header) — same button component as feat: "use my location" on maidenhead converter and channel editor #59.
  • Auto-prompt is not desired — always user gesture.

Channel detail page

When operator position is known and channel has useLocation + coordinates:

• Show distance from me in Location section (e.g. 12.4 km or 850 m — pick sensible threshold for unit switch).
• On embedded CodeplugMap: plot operator marker (distinct style from channel marker) plus channel marker; fit bounds or centre to show both when reasonable.
• When position unknown: show Use my location to enable distance; distance row hidden or "—".

Channel list

• Add sort control: Name (default) | Distance from me.
• Distance sort: channels with geolocation ascending by haversine distance; channels without location at bottom (stable sub-sort by name).
• Distance sort requires operator position — if unset, show helper + Use my location button; disable sort or prompt on select.
• Optional v1: Distance optional column when position known (defer if sort alone is enough).
• Channel list map (CodeplugMap at bottom of list): show operator marker when position set.

Zone detail map

• On zone detail CodeplugMap: show operator marker when position set (zone hull + member channels + you).
• No per-member distance table required for v1.

Distance math

• New util src/lib/geoDistance.ts (or extend src/lib/geo.ts): haversine distance in metres; format for display (formatDistanceM(m)).
• Use WGS84 coords throughout; no elevation.

Affected

• New useOperatorPosition hook or lightweight context (session state only)
• src/lib/geo.ts or geoDistance.ts — haversine + formatting
• src/routes/channels/detail.tsx — distance field, map operator marker
• src/routes/channels/list.tsx — sort control, optional map marker
• src/routes/zones/detail.tsx — map operator marker
• src/components/CodeplugMap/CodeplugMap.tsx — optional operatorPosition prop + marker rendering
• docs/features/maidenhead.md or map docs — session geolocation for browse vs edit

Notes / dependencies

• Builds on feat: "use my location" on maidenhead converter and channel editor #59 (UseMyLocationButton, useGeolocation, geolocation.ts) — reuse, don't fork.
• Operator position is ephemeral — distinct from channel location and from saving QTH in Settings (out of scope).
• Channels with hideFromMap still participate in distance sort/display if they have coordinates (hideFromMap affects map plots only — document behaviour).
• Privacy: position used only after explicit button click; not uploaded; session-only.

Out of scope

• Continuous GPS tracking / watchPosition while browsing.
• Bearing / compass direction to repeater.
• Filtering channel list by radius ("within 50 km") — sort is sufficient for v1.
• Persisting last known operator position across sessions.
• Summary page map (feat: revamp codeplug summary page with channel map and improved layout #61) — can follow same operatorPosition prop pattern later.

Manual verify

1. Channel detail → Use my location → distance appears; map shows two markers.
2. Deny permission → graceful message; no distance.
3. Channel list → sort by distance → nearest repeater first; unlocated channels last.
4. Zone detail map → operator marker visible alongside zone hull.
5. Reload page → operator position cleared (session); distance hidden until requested again.

Workflow note

Branch from origin/main, atomic conventional commits (distance util → operator position hook → CodeplugMap marker → detail → list sort → zone map → docs), PR linking Closes #70.

[pskillen]

Execution plan (Cursor)

Plan drafted for #70 — session operator position, distance on channel detail, proximity sort on channel list, operator marker on CodeplugMap (detail, list, zone).

Branch: 70/paddy/operator-distance from origin/main

Slices (commit at each checkpoint):

1. geoDistance.ts — haversine + formatDistanceM + tests
2. OperatorPositionProvider / useOperatorPosition — in-memory session state; wire in main.tsx
3. CodeplugMap — operatorPosition prop, distinct marker, include in bounds via collectMapPoints
4. Channel detail — distance row, Use my location / Clear, map prop
5. Channel list — Name | Distance sort + Use my location when needed; map marker
6. Zone detail — pass operator position to map
7. Docs — maidenhead.md, map README, progress/outstanding, sidecar updates

Deferred (per issue): distance table column on list, summary map (#61), bearing, radius filter, persistence, watchPosition.

PR: Closes #70 via user-github-personal MCP.

Executing agent: commit at every checkpoint before the next slice (overrides default commit-on-request rule).