Archive app-navigation and planner-multiplayer-awareness, sync specs

Both changes fully implemented. Sync delta specs to main:
- map-display: add Planner home page nav and cursor rendering requirements
- planner-session: add session participant awareness requirement

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

openspec/changes/app-navigation/design.md

@@ -1,40 +0,0 @@
-## Context
-
-Navigation audit found: Journal's `/routes` and `/activities` pages are
-orphaned (no links point to them). The Planner home page has no CTA. Logout
-is only on the profile page. Users must know URLs to use the apps.
-
-## Goals / Non-Goals
-
-**Goals:**
-- Every non-API route reachable via UI navigation
-- Logged-in Journal users see: Routes, Activities, profile, logout
-- Logged-out Journal users see: login, register
-- Planner home has a clear "start planning" action
-- Keep it minimal — a thin bar, not a complex sidebar
-
-**Non-Goals:**
-- Mobile hamburger menu (responsive PR already hides sidebar — nav bar wraps naturally)
-- Breadcrumbs or nested navigation
-- Settings page (future)
-
-## Decisions
-
-### D1: Journal nav bar in root Layout
-
-Add a `<nav>` element inside `Layout` in `root.tsx`. The root loader already
-returns the user (added for Sentry context), so the nav bar can conditionally
-show authenticated vs. unauthenticated links. No new loader needed.
-
-### D2: Planner gets a CTA on home, not a nav bar
-
-The Planner is session-focused — users arrive, create a session, and work in
-it. A full nav bar would be overhead. Instead: home page gets a prominent
-"Start Planning" button linking to `/new`. Session view already has a header —
-add a small logo/home link to it.
-
-### D3: Use @trails-cool/ui for shared nav component
-
-The nav bar itself is Journal-specific (routes, activities, auth). No need
-to put it in the shared UI package — it goes directly in Journal's root.tsx
-or a colocated component.