feat: resolve 7 pre-ship QoL items

- Space/Shift+Space: page down/up in detail panel (80% scroll)
- Content font: sans-serif/serif/monospace selector in appearance
  settings, applied to article content in detail panel
- Accessibility: entry-list-item uses button instead of div, folder
  toggles have aria-expanded, shortcut keys have aria-labels
- Share notes: replaced window.prompt with proper modal dialog
  matching existing UI patterns
- Worker .env.example: template with all 10 environment variables
- Worker poisoned messages: archive unprocessable queue messages
  instead of leaving them stuck forever
- Worker pool Submit: check return value, reschedule dropped feeds
  30s into the future, log warnings for rejected submissions

2 files changed, 22 insertions, 0 deletions

diff --git a/apps/web/lib/hooks/use-keyboard-navigation.ts b/apps/web/lib/hooks/use-keyboard-navigation.ts
index 24a4761..8685396 100644
--- a/apps/web/lib/hooks/use-keyboard-navigation.ts
+++ b/apps/web/lib/hooks/use-keyboard-navigation.ts
@@ -368,6 +368,7 @@ export function useKeyboardNavigation() {
 
     function handleDetailPanelKeyDown(event: KeyboardEvent) {
       const SCROLL_AMOUNT = 100
+      const PAGE_SCROLL_FRACTION = 0.8
       const detailArticle = document.querySelector<HTMLElement>(
         "[data-detail-article]"
       )
@@ -385,6 +386,19 @@ export function useKeyboardNavigation() {
           if (detailArticle) detailArticle.scrollTop -= SCROLL_AMOUNT
           break
         }
+        case " ": {
+          event.preventDefault()
+          if (detailArticle) {
+            const pageScrollAmount =
+              detailArticle.clientHeight * PAGE_SCROLL_FRACTION
+            if (event.shiftKey) {
+              detailArticle.scrollTop -= pageScrollAmount
+            } else {
+              detailArticle.scrollTop += pageScrollAmount
+            }
+          }
+          break
+        }
         case "?": {
           event.preventDefault()
           toggleShortcutsDialog()
diff --git a/apps/web/lib/stores/user-interface-store.ts b/apps/web/lib/stores/user-interface-store.ts
index 01dceba..fdee347 100644
--- a/apps/web/lib/stores/user-interface-store.ts
+++ b/apps/web/lib/stores/user-interface-store.ts
@@ -7,6 +7,8 @@ type DisplayDensity = "compact" | "default" | "spacious"
 
 type FontSize = "small" | "default" | "large"
 
+type ContentFont = "sans-serif" | "serif" | "monospace"
+
 type TimeDisplayFormat = "relative" | "absolute"
 
 type FocusedPanel = "sidebar" | "entryList" | "detailPanel"
@@ -38,6 +40,7 @@ interface UserInterfaceState {
   showFeedFavicons: boolean
   focusFollowsInteraction: boolean
   fontSize: FontSize
+  contentFont: ContentFont
   timeDisplayFormat: TimeDisplayFormat
   showEntryImages: boolean
   showReadingTime: boolean
@@ -62,6 +65,7 @@ interface UserInterfaceState {
   setShowFeedFavicons: (show: boolean) => void
   setFocusFollowsInteraction: (enabled: boolean) => void
   setFontSize: (size: FontSize) => void
+  setContentFont: (font: ContentFont) => void
   setTimeDisplayFormat: (format: TimeDisplayFormat) => void
   setShowEntryImages: (show: boolean) => void
   setShowReadingTime: (show: boolean) => void
@@ -90,6 +94,7 @@ export const useUserInterfaceStore = create<UserInterfaceState>()(
       showFeedFavicons: true,
       focusFollowsInteraction: false,
       fontSize: "default",
+      contentFont: "sans-serif",
       timeDisplayFormat: "relative",
       showEntryImages: true,
       showReadingTime: true,
@@ -134,6 +139,8 @@ export const useUserInterfaceStore = create<UserInterfaceState>()(
 
       setFontSize: (size) => set({ fontSize: size }),
 
+      setContentFont: (font) => set({ contentFont: font }),
+
       setTimeDisplayFormat: (format) => set({ timeDisplayFormat: format }),
 
       setShowEntryImages: (show) => set({ showEntryImages: show }),
@@ -187,6 +194,7 @@ export const useUserInterfaceStore = create<UserInterfaceState>()(
         focusFollowsInteraction: state.focusFollowsInteraction,
         expandedFolderIdentifiers: state.expandedFolderIdentifiers,
         fontSize: state.fontSize,
+        contentFont: state.contentFont,
         timeDisplayFormat: state.timeDisplayFormat,
         showEntryImages: state.showEntryImages,
         showReadingTime: state.showReadingTime,