Polish pass 8 — console → debug, sentence case, attachment button

- core.ts, feed.ts, user.ts: replace all console.log/warn/error with
  debug.log/warn/error (silent in production builds)
- ArticleFeed: "write article" → "Write article"
- ComposeBox: attachment remove x → ×, add aria-label

src/components/article/ArticleFeed.tsx

@@ -70,7 +70,7 @@ export function ArticleFeed() {
           onClick={() => setView("article-editor")}
           className="text-[11px] px-3 py-1 border border-accent/60 text-accent hover:bg-accent hover:text-accent-text transition-colors"
         >
-          write article
+          Write article
         </button>
       </header>
 

src/components/feed/ComposeBox.tsx

@@ -272,8 +272,9 @@ export function ComposeBox({ onPublished, onNoteInjected }: { onPublished?: () =
                     onClick={() => removeAttachment(i)}
                     className="absolute -top-1.5 -right-1.5 w-4 h-4 bg-danger text-white text-[10px] rounded-full flex items-center justify-center opacity-0 group-hover:opacity-100 transition-opacity"
                     title="Remove"
+                    aria-label="Remove attachment"
                   >
-                    x
+                    ×
                   </button>
                 </div>
               ))}