feat(ui): replace unicode icons with solid-icons

Swap emoji and unicode glyphs for Tabler components so icons inherit
currentColor and font-size and render consistently across platforms.

- add src/components/doc-icons.ts to resolve doc-entry frontmatter icon
  keys to components; frontmatter now stores semantic keys
- replace the align-*.png assets with TbOutlineAlign* icons
- render RevealManager action SVGs as components instead of injected
  innerHTML strings
- carry completion icons via an optional CompletionItem.icon field

src/components/journal/ErrorPopup.tsx

@@ -3,6 +3,7 @@
  * the journal input area. Toggled by clicking the truncated error text.
  */
 import { Component, Show } from "solid-js";
+import { TbOutlineX } from "solid-icons/tb";
 
 interface ErrorPopupProps {
   message: string | null;
@@ -21,7 +22,7 @@ export const ErrorPopup: Component<ErrorPopupProps> = (props) => {
             class="text-red-400 hover:text-red-600 text-xs leading-none ml-2 shrink-0"
             title="关闭"
           >
-            ✕
+            <TbOutlineX />
           </button>
         </div>
       </div>