feat: clipboard paste for per-annotation images & fix absolute path resolution (#255)

Add capture-phase paste listener to AttachmentsButton so users can
Cmd+V / Ctrl+V images directly into per-annotation attachments when
the popover is open. Uses stopPropagation to prevent the global paste
handler in App.tsx from also processing the event. Adds a platform-aware
keyboard shortcut hint in the drop zone.

Also fixes a regression from #237 where resolveMarkdownFile rejected
absolute paths outside the project root. The original behavior allowed
any absolute path the user explicitly provided; the security boundary
should only apply to relative path / bare filename search.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dgrissen2

packages/server/resolve-file.ts

@@ -42,12 +42,10 @@ export async function resolveMarkdownFile(
     return { kind: "not_found", input };
   }
 
-  // 1. Absolute path — use as-is
+  // 1. Absolute path — use as-is (no project root restriction;
+  //    the user explicitly typed the full path)
   if (input.startsWith("/")) {
     const normalized = resolve(input);
-    if (!normalized.startsWith(projectRoot + "/") && normalized !== projectRoot) {
-      return { kind: "not_found", input };
-    }
     if (await Bun.file(normalized).exists()) {
       return { kind: "found", path: normalized };
     }

packages/ui/components/AttachmentsButton.tsx

@@ -87,6 +87,28 @@ export const AttachmentsButton: React.FC<AttachmentsButtonProps> = ({
     return () => window.removeEventListener('keydown', handleKeyDown);
   }, [isOpen]);
 
+  // Paste image from clipboard when popover is open (per-annotation attachments).
+  // Uses capture phase + stopPropagation to prevent the global paste handler in
+  // App.tsx from also processing the same event.
+  useEffect(() => {
+    if (!isOpen || annotatorImage) return;
+    const handlePaste = (e: ClipboardEvent) => {
+      const items = e.clipboardData?.items;
+      if (!items) return;
+      for (const item of items) {
+        if (item.type.startsWith('image/')) {
+          e.preventDefault();
+          e.stopPropagation();
+          const file = item.getAsFile();
+          if (file) handleFileSelect(file);
+          return;
+        }
+      }
+    };
+    document.addEventListener('paste', handlePaste, true);
+    return () => document.removeEventListener('paste', handlePaste, true);
+  }, [isOpen, annotatorImage]);
+
   const handleFileSelect = (file: File) => {
     // Derive name before opening annotator so user sees it immediately
     const initialName = deriveImageName(file.name, images.map(i => i.name));
@@ -295,6 +317,9 @@ export const AttachmentsButton: React.FC<AttachmentsButtonProps> = ({
                     <span className="text-xs text-muted-foreground">
                       Drop image or click to browse
                     </span>
+                    <span className="text-[10px] text-muted-foreground/70">
+                      {navigator.platform?.includes('Mac') ? '⌘' : 'Ctrl'}+V to paste from clipboard
+                    </span>
                   </>
                 )}
               </div>