chore: migrate docsearch and imagescript to npm/jsr imports (#3732)

## Summary
- **docsearch**: Replaced `esm.sh` URL with `npm:@docsearch/js@^3.5.2`.
Added a type cast workaround in `SearchButton.tsx` since Deno's type
checker treats this npm package as CJS (missing `"type": "module"`).
- **imagescript**: Replaced `deno.land/x` URL with
`jsr:@matmen/imagescript@^1.3.0`. Clean swap, no code changes needed.

These were legacy URL-based imports from before Deno had native `npm:`
and `jsr:` support.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju

deno.json

@@ -54,7 +54,7 @@
     "@types/node": "npm:@types/node@^24.3.0",
     "@types/pg": "npm:@types/pg@^8.15.5",
     "@types/prismjs": "npm:@types/prismjs@^1.26.5",
-    "docsearch": "https://esm.sh/@docsearch/js@3.5.2?target=es2020",
+    "docsearch": "npm:@docsearch/js@^3.5.2",
     "esbuild": "npm:esbuild@0.25.7",
     "esbuild-wasm": "npm:esbuild-wasm@0.25.7",
     "fresh": "jsr:@fresh/core@^2.0.0",
@@ -91,7 +91,7 @@
 
     "@std/front-matter": "jsr:@std/front-matter@^1.0.5",
     "github-slugger": "npm:github-slugger@^2.0.0",
-    "imagescript": "https://deno.land/x/imagescript@1.3.0/mod.ts",
+    "imagescript": "jsr:@matmen/imagescript@^1.3.0",
     "marked": "npm:marked@^15.0.11",
     "marked-mangle": "npm:marked-mangle@^1.1.9",
     "prismjs": "npm:prismjs@^1.29.0",

deno.lock

@@ -1,5 +1,5 @@
 import { useEffect, useRef } from "preact/hooks";
-import docsearch from "docsearch";
+import docsearchModule from "docsearch";
 
 // Copied from algolia source code
 type DocSearchProps = {
@@ -9,6 +9,11 @@ type DocSearchProps = {
   container: HTMLElement | string;
 };
 
+// Workaround: Deno resolves this npm package as CJS, hiding the callable default export
+const docsearch = docsearchModule as unknown as (
+  props: DocSearchProps,
+) => void;
+
 export default function SearchButton(
   props: { docsearch?: (args: DocSearchProps) => void; class?: string },
 ) {