Rough edges: mobile 100dvh, session-expiry in chat, sticky error toasts, journal date filter (#85)

The safe, self-contained wins from the #85 bundle:

- **Mobile viewport.** The editor used `100vh`, which on mobile Safari/Chrome is
  the LARGEST viewport (URL bar hidden), so with the bar visible the canvas
  bottom and Fit button were pushed under the browser chrome. `100dvh` fixes it.
- **Session expiry mid-chat.** A 401 during a chat turn was mapped to "the
  assistant is not available right now" — sending the user to debug a config
  problem that isn't there. Now it says the session expired and redirects to
  /login, preserving the path, like the rest of the app treats 401.
- **Error toasts persist.** Error toasts were the primary report that a mutation
  failed, yet auto-dismissed at 4s with no way to retrieve them — look away and
  it's gone. Errors now stay until dismissed; info toasts still time out; both
  get a close button.
- **Journal date filter.** `from`/`to` existed in the API and JournalFilter but
  had no UI, so "show me last spring" was unreachable. Added two date inputs
  (with a Clear) that feed the existing filter. No backend change.

Deferred to their own follow-ups (too big for this bundle, or need a decision):
revision-history retention/pruning, the agent toolbox's missing corrective tools,
plop-level journal entries from the UI, and the editor's max-width cap (a layout
call worth confirming rather than changing blind). The DESIGN.md API-listing
drift the issue mentioned was already fixed in #89.

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

web/src/editor/JournalPanel.tsx

@@ -42,7 +42,15 @@ export function JournalPanel({
   scopeObjectId: number | null
   onScopeChange: (id: number | null) => void
 }) {
-  const filter = scopeObjectId != null ? { objectId: scopeObjectId } : {}
+  // Date-range narrowing (#85): the backend and JournalFilter already supported
+  // from/to; they just had no UI. Empty inputs don't filter.
+  const [from, setFrom] = useState('')
+  const [to, setTo] = useState('')
+  const filter = {
+    ...(scopeObjectId != null ? { objectId: scopeObjectId } : {}),
+    ...(from ? { from } : {}),
+    ...(to ? { to } : {}),
+  }
   const journal = useJournal(gardenId, filter)
   const entries = journal.data?.pages.flatMap((p) => p.entries) ?? []
   const scopedObject = objects.find((o) => o.id === scopeObjectId) ?? null
@@ -70,6 +78,41 @@ export function JournalPanel({
         )}
       </div>
 
+      <div className="flex items-center gap-2 text-xs text-muted">
+        <label className="flex items-center gap-1">
+          <span>From</span>
+          <input
+            type="date"
+            value={from}
+            max={to || undefined}
+            onChange={(e) => setFrom(e.target.value)}
+            className="rounded-md border border-border bg-surface px-1.5 py-1 text-fg outline-none focus-visible:ring-2 focus-visible:ring-accent/40"
+          />
+        </label>
+        <label className="flex items-center gap-1">
+          <span>To</span>
+          <input
+            type="date"
+            value={to}
+            min={from || undefined}
+            onChange={(e) => setTo(e.target.value)}
+            className="rounded-md border border-border bg-surface px-1.5 py-1 text-fg outline-none focus-visible:ring-2 focus-visible:ring-accent/40"
+          />
+        </label>
+        {(from || to) && (
+          <button
+            type="button"
+            onClick={() => {
+              setFrom('')
+              setTo('')
+            }}
+            className="rounded px-1 text-muted outline-none hover:text-fg focus-visible:ring-2 focus-visible:ring-accent/40"
+          >
+            Clear
+          </button>
+        )}
+      </div>
+
       {canEdit && (
         <Composer
           gardenId={gardenId}