design: extend with single-panel architecture (Phases k-o)

Adds the broader panel design that consolidates today's two-panel
layout (Routes/Contacts + floating PlaceDetail) into one always-visible
left column with state-driven content. Defines five panel states
(IDLE, PREVIEW, ROUTING, PREVIEW+ROUTING, ROUTE_CALCULATED), shared
place-card component, search bar behavior including aspirational
search history, and implementation phases k-o.

NAVI-DIRECTIONS-REDESIGN.md

@@ -508,6 +508,9 @@ Separate session will address:
 | Multi-modal | Drive + transit + walk hybrids |
 | Traffic-aware routing | Requires traffic data source |
 | Offline routing | Requires local Valhalla instance |
+| Search history backend persistence | Frontend localStorage first |
+| Saved places browsing UI | Future dedicated work |
+| Contacts view redesign | Separate from route-building |
 
 ---
 
@@ -526,7 +529,17 @@ Separate session will address:
 | **i** | Add map-click-to-fill-active-input | e |
 | **j** | Mobile polish (long-press timing, bottom sheet, keyboard) | a-i |
 
-**Estimated phases:** 10 discrete tasks, can be done incrementally.
+### Phases k-o: Single-Panel Architecture
+
+| Phase | Task | Depends On |
+|-------|------|------------|
+| **k** | Refactor Panel.jsx to single-column state-driven content, remove right PlaceDetail panel | — |
+| **l** | Build shared place card component (preview + stop cards) | k |
+| **m** | Wire panel state transitions (IDLE → PREVIEW → ROUTING → ROUTE_CALCULATED) | l |
+| **n** | Mobile bottom sheet state mapping | m |
+| **o** | Search history (frontend localStorage scope first) | m |
+
+**Estimated phases:** 15 discrete tasks, can be done incrementally.
 
 ---
 
@@ -622,6 +635,168 @@ Future expansion via contextual wedge sets (different actions based on what was
 - Long-press / contextmenu handler always opens radial
 - Radial "Directions from/to here" explicitly sets input, overriding prior value
 
+---
+
+## 15. Panel Architecture (Single-Column Model)
+
+This section defines the broader panel design that consolidates today's
+two-panel layout (Routes/Contacts + floating PlaceDetail) into one
+always-visible left column with state-driven content.
+
+### Overview
+
+The left panel is one always-visible column with state-driven content.
+The right-side PlaceDetail panel is **removed**; its content moves into
+the left panel.
+
+**Width:** ~360px desktop. Mobile: panel becomes bottom sheet per
+Section 10.
+
+**Visual style:** Panel is always anchored at the left edge of the
+viewport with consistent panel background. When idle (no preview, no
+route), only the search bar is visible at the top — the rest of the
+panel is empty space. The panel never disappears; it just shows less
+or more content depending on state.
+
+### Panel States
+
+Panel states are mutually exclusive content modes:
+
+#### IDLE (no preview, no route)
+
+- Search bar at top
+- Empty body (or subtle empty-state prompt: "Search or click a place
+  to begin")
+- Recent activity / search history (when implemented)
+
+#### PREVIEW (place selected via map click or search, not committed to route)
+
+- Search bar at top
+- Preview card: full place detail (name, type, coords, elevation,
+  land class, about, contact, links)
+- Action buttons inside or below the card: [Directions] [Add stop]
+  [Save] [Share] [x]
+- Click another place: preview replaced (previous lost — search
+  history retains it)
+- Click x or Escape: preview dismissed, return to IDLE
+
+#### ROUTING (1+ stops, no preview)
+
+- Search bar at top
+- Section: "Route" with stop cards
+- Each stop card: collapsed by default (header: pin + name +
+  drag handle + remove); expandable to show full detail
+- Drag-to-reorder via card headers (preserves existing StopList)
+- Per-card actions: Save, Share, Remove
+- Bottom: [Get Directions] (when 2+ stops with valid mode), mode
+  selector (auto/walk/bike), trip summary placeholder
+
+#### PREVIEW + ROUTING (place clicked while route exists)
+
+- Search bar at top
+- Preview card directly below search
+- Route section below preview
+- Both visible simultaneously
+- Multiple cards can be expanded at once (preview + a stop)
+
+#### ROUTE_CALCULATED (after route fetch)
+
+- Search bar at top
+- Route summary (total time, distance)
+- Mode selector
+- Stop cards (collapsed; expand for detail)
+- Turn-by-turn maneuvers
+- Preview can appear on top if user clicks a place
+
+### Search Bar Behavior
+
+- Pinned to top of panel
+- Always for browsing (search -> preview, never auto-add as stop)
+
+#### Search History (aspirational — design now, implement later)
+
+- Empty search -> dropdown shows 5 most recent searches
+- Authed: persisted to backend
+- Guest: localStorage
+- Typing: recent matches sorted to top of search results
+
+### Card Pattern
+
+Shared between preview and stop cards. Both use the same component,
+parameterized by role.
+
+#### Header (always visible)
+
+- Pin/marker icon (color varies by role — preview vs stop number)
+- Place name
+- Expand/collapse chevron
+- For stops: drag handle, remove (x)
+
+#### Body (collapsed by default for stops, expanded by default for preview)
+
+- Type / category
+- Coordinates + elevation + land class
+- About (description, Wikipedia excerpt)
+- Contact (phone, website, hours)
+- Links (Wikipedia, OSM, Wikidata)
+- Action buttons:
+  - Preview: [Directions] [Add stop] [Save] [Share]
+  - Stop: [Save] [Share]
+
+### State Transitions
+
+```
+IDLE -> PREVIEW                   : click place / search-select
+PREVIEW -> IDLE                   : x button / Escape
+PREVIEW -> PREVIEW (different)    : click another place
+PREVIEW -> ROUTING                : "Add stop" on preview
+PREVIEW -> ROUTE_CALCULATED       : "Directions" (becomes destination,
+                                    route auto-calculates if From available)
+ROUTING -> IDLE                   : remove all stops
+ROUTING -> PREVIEW + ROUTING      : click place
+ROUTING -> ROUTE_CALCULATED       : "Get Directions" / auto-route trigger
+PREVIEW + ROUTING -> ROUTING      : dismiss preview
+PREVIEW + ROUTING -> ROUTING      : "Add stop" on preview (adds new stop)
+ROUTE_CALCULATED -> ROUTING       : edit route
+ROUTE_CALCULATED -> IDLE          : clear route
+```
+
+### Routes / Contacts Tabs
+
+Tentative: Routes is default panel. Contacts is a separate view
+accessible via a tab or icon at the top. Contacts view replaces
+route/preview content with a contact list — does not combine with
+route-building.
+
+### Map Zoom-to-Feature
+
+With single panel, padding becomes simpler — just one panel width
+(~360px) on the left. Top/right/bottom can be small (~50px each).
+
+### Mobile Bottom Sheet State Mapping
+
+Same logic as desktop, layout rotated:
+
+| State               | Sheet Position |
+|---------------------|----------------|
+| IDLE                | peek (search bar visible) |
+| PREVIEW             | half (preview card) |
+| ROUTING             | half (stops list) |
+| PREVIEW + ROUTING   | full (both, scrollable) |
+| ROUTE_CALCULATED    | half/full (summary + maneuvers) |
+
+---
+
+## 16. Open Questions
+
+### From Single-Panel Architecture
+
+- Routes/Contacts tab location and behavior in single-panel model
+- Preview-of-already-routed-place: probably auto-expands the existing
+  stop card, no duplicate preview
+- Preview card position confirmed above route section (per mock)
+
+
 ---
 
 ## Appendix A: Current Code References
@@ -664,4 +839,4 @@ Future expansion via contextual wedge sets (different actions based on what was
 
 ---
 
-*Document created 2026-04-26. Updated 2026-04-26 with resolved decisions. Implementation to follow in dedicated session.*
+*Document created 2026-04-26. Updated with resolved decisions and single-panel architecture (Phases k-o). Implementation to follow in dedicated session.*