Archive elevation-map-interaction, sync spec to main

Synced new spec (chart ↔ map interaction, mobile touch, iOS safe area,
responsive header) to openspec/specs/elevation-map-interaction/.

All 4 artifacts complete. All 14 tasks complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/specs/elevation-map-interaction/spec.md

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+## ADDED Requirements
+
+### Requirement: Route hover highlights elevation chart
+Hovering over the route polyline on the map SHALL highlight the corresponding position on the elevation chart.
+
+#### Scenario: Hover route on map
+- **WHEN** a user hovers over the route polyline on the map
+- **THEN** the elevation chart shows a crosshair at the corresponding distance along the route
+
+#### Scenario: Leave route on map
+- **WHEN** a user moves the mouse away from the route polyline
+- **THEN** the elevation chart crosshair disappears
+
+### Requirement: Chart click pans map
+Clicking on the elevation chart SHALL pan the map to center on that point along the route.
+
+#### Scenario: Click chart
+- **WHEN** a user clicks on the elevation chart
+- **THEN** the map pans to center on the corresponding route coordinate
+
+### Requirement: Chart drag-select zooms map
+Dragging a range on the elevation chart SHALL zoom the map to fit that section of the route.
+
+#### Scenario: Drag select range
+- **WHEN** a user clicks and drags horizontally on the elevation chart
+- **THEN** a visual highlight shows the selected range
+- **AND** on mouse release, the map zooms to fit the route coordinates within that range
+
+#### Scenario: Reset zoom
+- **WHEN** the map has been zoomed via chart drag-select
+- **THEN** a reset button appears to return to the full route view
+
+### Requirement: Mobile touch interaction
+The elevation chart SHALL support touch-based interaction on mobile devices.
+
+#### Scenario: Single touch scrub
+- **WHEN** a user touches and drags on the chart with one finger
+- **THEN** the crosshair follows the finger position along the chart
+- **AND** the map highlight dot follows in real-time
+
+#### Scenario: Tap to pan
+- **WHEN** a user taps the chart (touch without significant movement)
+- **THEN** the map pans to that point along the route
+
+#### Scenario: Two-finger range select
+- **WHEN** a user places two fingers on the chart
+- **THEN** the area between the fingers is highlighted as a selection range
+- **AND** on release, the map zooms to fit the route coordinates in that range
+
+#### Scenario: No page scroll on touch
+- **WHEN** a user touches the elevation chart
+- **THEN** page scrolling is prevented (touch-none CSS + preventDefault)
+
+### Requirement: iOS safe area support
+The Planner layout SHALL respect iOS safe area insets.
+
+#### Scenario: Notch/Dynamic Island clearance
+- **WHEN** the Planner is viewed on an iOS device with a notch or Dynamic Island
+- **THEN** the header bar is padded below the safe area inset
+
+#### Scenario: Home indicator clearance
+- **WHEN** the Planner is viewed on an iOS device without a physical home button
+- **THEN** the elevation chart area is padded above the home indicator
+
+#### Scenario: No accidental page zoom
+- **WHEN** a user pinches on the Planner UI
+- **THEN** the browser-level page zoom does not trigger (viewport user-scalable=no)
+
+### Requirement: Responsive mobile header
+The Planner header SHALL adapt to small screens by hiding secondary controls.
+
+#### Scenario: Small screen header
+- **WHEN** the Planner is viewed on a mobile device
+- **THEN** only the profile selector and export button are visible
+- **AND** participant list, undo/redo, connection status, and computing text are hidden
+
+#### Scenario: Desktop header
+- **WHEN** the Planner is viewed on a desktop screen
+- **THEN** all header controls are visible