Reclaim mobile chrome: drop the editor's top banner, un-cramp the assistant

Two mobile complaints, both in the editor/assistant context:

- The global top bar (brand + account) sat above the editor's own
  garden-name strip — a whole banner of pure chrome over a full-screen
  canvas. Hide it on mobile in the editor (the same rationale that hides
  the bottom nav there) and fold a leaf/back affordance into the garden
  strip so there's still a way out. Desktop keeps the header. The editor's
  height band shrinks 8rem → 4rem on mobile to hand that space to the
  canvas; desktop stays 8rem since the header is still there.

- The assistant (and journal/history) rendered inside the rail peek
  capped at max-h-[50vh]; after the tab bar, header and input, messages
  got ~200px. That cap is right for the inspector (read alongside the
  canvas) but not for a mode where reading/typing is the task. Panel
  modes now take a taller slice (78vh) via a `tall` prop; the inspector
  keeps the 50vh peek. Chat message spacing loosened gap-2 → gap-3.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

web/src/pages/GardenEditorPage.tsx

@@ -1,5 +1,5 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
-import { getRouteApi } from '@tanstack/react-router'
+import { Link, getRouteApi } from '@tanstack/react-router'
 import { Alert } from '@/components/ui/Alert'
 import { Button } from '@/components/ui/Button'
 import { GardenCanvas } from '@/editor/GardenCanvas'
@@ -544,8 +544,13 @@ export function GardenEditorPage() {
   // 100dvh, not 100vh: on mobile Safari/Chrome 100vh is the *largest* viewport
   // (URL bar hidden), so with the bar showing the editor overflowed and pushed
   // the canvas bottom + Fit button under the browser chrome (#85).
+  //
+  // The subtracted band differs by breakpoint because the chrome does. On mobile
+  // the global top bar is hidden here (AppShell), so only <main>'s padding is
+  // above us — 4rem reclaims the ~48px the header used to cost the canvas. On
+  // desktop the header is present, so keep the original 8rem.
   return (
-    <div className="flex h-[calc(100dvh-8rem)] flex-col gap-3 md:flex-row">
+    <div className="flex h-[calc(100dvh-4rem)] flex-col gap-3 md:h-[calc(100dvh-8rem)] md:flex-row">
       {/* Desktop-only control column. On mobile these move to the bottom mode bar
           + a slim top strip so the canvas — the point of the screen — isn't shoved
           into a corner by a stack of controls (#99). */}
@@ -597,8 +602,17 @@ export function GardenEditorPage() {
 
       <div className="relative flex min-h-0 flex-1 flex-col gap-2">
         {/* Mobile top strip: the garden identity / season / share that live in the
-            desktop left column. md:hidden. */}
+            desktop left column, plus the way out. The global header is hidden on
+            mobile here (AppShell), so this leaf is the only route back to the
+            gardens list — it can't be dropped. md:hidden. */}
         <div className="flex items-center gap-2 md:hidden">
+          <Link
+            to="/gardens"
+            aria-label="All gardens"
+            className="-ml-1 shrink-0 rounded-md px-1.5 py-1 text-lg leading-none text-accent-strong outline-none focus-visible:ring-2 focus-visible:ring-accent/40"
+          >
+            🌱
+          </Link>
           <h1 className="min-w-0 flex-1 truncate text-base font-semibold tracking-tight" title={garden.name}>
             {garden.name}
           </h1>
@@ -673,6 +687,11 @@ export function GardenEditorPage() {
           tabs={railTabs}
           activeId={railTab}
           onActivate={setRailTab}
+          // The inspector is read alongside the canvas, so it stays a half-height
+          // peek. Journal/History/Assistant are the task themselves — reading and
+          // typing want room — so they take a taller slice on mobile (the canvas
+          // above just needs to stay glanceable as the assistant edits it).
+          tall={railTab !== 'inspector'}
           onClose={() => {
             // Only the inspector is *about* the selection, so only closing it
             // deselects; dismissing a panel leaves the canvas as you had it. Any