Break up route-features into focused specs, add new changes

Archive the monolithic route-features spec and replace with 9 focused
OpenSpec changes: multi-day-routes, waypoint-notes (with POI snapping),
undo-redo, local-dev-stack, route-sharing, route-discovery,
activity-photos, osm-overlays, plus the existing changelog and
komoot-import.

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

openspec/changes/undo-redo/proposal.md

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+## Why
+
+Route editing mistakes in the Planner have no recovery path. Accidentally
+deleting a waypoint, dragging to the wrong spot, or removing a no-go area
+requires manually recreating the change. This is especially frustrating during
+complex multi-waypoint edits where a single misclick can undo minutes of work.
+
+Every desktop editing tool supports Ctrl+Z. Users expect it. Its absence is
+the most obvious missing affordance in the Planner.
+
+## What Changes
+
+- Add undo/redo support to the Planner's route editor using Yjs's built-in
+  `UndoManager`
+- Keyboard shortcuts: Ctrl+Z (undo), Ctrl+Shift+Z / Ctrl+Y (redo)
+- Undo/redo buttons in the topbar with disabled state when the stack is empty
+- Only the current user's changes are undone -- collaborative-safe by design.
+  Other participants' edits are never affected by your undo.
+
+## Scope
+
+Tracked types:
+- `waypoints` (Y.Array) -- add, remove, reorder, drag-move
+- `noGoAreas` (Y.Array) -- add, remove
+- `notes` (Y.Text) -- text edits
+
+`routeData` (Y.Map) is **not** tracked. It contains derived data (route
+geometry, segment boundaries) computed by BRouter, not direct user input.
+Undoing a waypoint change will trigger a re-route automatically.
+
+## Non-Goals
+
+- Infinite undo history -- UndoManager keeps a reasonable in-memory stack,
+  no persistence needed
+- Undo across sessions -- the undo stack is in-memory and resets when
+  the page is closed or the WebSocket reconnects
+- Undo for route options (profile selection, color mode) -- these are
+  infrequent, low-risk changes that don't warrant undo tracking
+- Granular undo for individual keystrokes in notes -- Y.Text undo groups
+  by capture timeout, which is good enough
+
+## Capabilities
+
+### New Capabilities
+
+- `undo-redo`: Undo/redo for route editing operations in the Planner via
+  keyboard shortcuts and topbar buttons, scoped to the local user's changes
+
+### Modified Capabilities
+
+(None)
+
+## Impact
+
+- **Files**: New hook (`use-undo.ts`), modified `use-yjs.ts` (transaction
+  origins), modified `SessionView.tsx` (buttons + keyboard handler), modified
+  mutation sites in `PlannerMap.tsx`, `WaypointSidebar.tsx`,
+  `NoGoAreaLayer.tsx`, `NotesPanel.tsx`
+- **Dependencies**: None -- Yjs `UndoManager` is built into the `yjs` package
+  already in use
+- **i18n**: Tooltip strings for undo/redo buttons