perf(code): replace react-syntax-highlighter and prismjs with the Shiki worker

Route all non-markdown code highlighting through the off-main-thread Shiki
worker, removing react-syntax-highlighter and prismjs entirely.

- Extend the worker with highlightLines: tokenize a whole block once and return
  per-line inner HTML, so per-line layouts (diffs, gutters, virtualization) make
  one worker call instead of one highlighter per line.
- Add shared WorkerHighlightedCode (whole-block) and useWorkerHighlightedLines
  (per-line) primitives. Colors resolve via the --md-syntax-* CSS variables, so
  theme changes never re-highlight.
- Migrate all 12 react-syntax-highlighter call sites: PermissionCard,
  ToolPart, ContextSidebarTab, ToolOutputDialog (whole block) and
  DiffPreview/WritePreview (per line).
- Migrate VirtualizedCodeBlock off prismjs to the worker, keeping virtua
  virtualization; whole-block tokenization also restores cross-line syntax
  context that per-line highlighting lost.
- Drop react-syntax-highlighter (+types) from ui and web, prismjs (+types) from
  ui, and the orphaned create-element type shim.

bun.lock

@@ -149,7 +149,6 @@
         "@pierre/diffs": "1.3.0-beta.4",
         "@replit/codemirror-vim": "^6.3.0",
         "@simplewebauthn/browser": "13.3.0",
-        "@types/react-syntax-highlighter": "^15.5.13",
         "@xenova/transformers": "^2.17.2",
         "@zumer/snapdom": "^2.12.0",
         "beautiful-mermaid": "^1.1.3",
@@ -169,12 +168,10 @@
         "morphdom": "^2.7.7",
         "motion": "^12.23.24",
         "next-themes": "^0.4.6",
-        "prismjs": "^1.30.0",
         "qrcode": "^1.5.4",
         "react": "^19.1.1",
         "react-dom": "^19.1.1",
         "react-drawio": "1.0.7",
-        "react-syntax-highlighter": "^15.6.6",
         "rehype-katex": "^7.0.1",
         "remark-math": "^6.0.0",
         "remend": "^1.2.1",
@@ -193,7 +190,6 @@
         "@remixicon/react": "^4.7.0",
         "@tailwindcss/postcss": "^4.0.0",
         "@types/node": "^24.3.1",
-        "@types/prismjs": "^1.26.6",
         "@types/qrcode": "^1.5.5",
         "@types/react": "^19.1.10",
         "@types/react-dom": "^19.1.7",
@@ -292,7 +288,6 @@
         "@types/node": "^24.3.1",
         "@types/react": "^19.1.10",
         "@types/react-dom": "^19.1.7",
-        "@types/react-syntax-highlighter": "^15.5.13",
         "@types/supertest": "^7.2.0",
         "@vitejs/plugin-react": "^5.0.0",
         "autoprefixer": "^10.4.21",
@@ -312,7 +307,6 @@
         "react": "^19.1.1",
         "react-dom": "^19.1.1",
         "react-markdown": "^10.1.0",
-        "react-syntax-highlighter": "^15.6.6",
         "remark-gfm": "^4.0.1",
         "sonner": "^2.0.7",
         "strip-json-comments": "^5.0.3",
@@ -1316,8 +1310,6 @@
 
     "@types/plist": ["@types/plist@3.0.5", "", { "dependencies": { "@types/node": "*", "xmlbuilder": ">=11.0.1" } }, "sha512-E6OCaRmAe4WDmWNsL/9RMqdkkzDCY1etutkflWk4c+AcjDU07Pcz1fQwTX0TQz+Pxqn9i4L1TU3UFpjnrcDgxA=="],
 
-    "@types/prismjs": ["@types/prismjs@1.26.6", "", {}, "sha512-vqlvI7qlMvcCBbVe0AKAb4f97//Hy0EBTaiW8AalRnG/xAN5zOiWWyrNqNXeq8+KAuvRewjCVY1+IPxk4RdNYw=="],
-
     "@types/qrcode": ["@types/qrcode@1.5.6", "", { "dependencies": { "@types/node": "*" } }, "sha512-te7NQcV2BOvdj2b1hCAHzAoMNuj65kNBMz0KBaxM6c3VGBOhU0dURQKOtH8CFNI/dsKkwlv32p26qYQTWoB5bw=="],
 
     "@types/react": ["@types/react@19.2.14", "", { "dependencies": { "csstype": "^3.2.2" } }, "sha512-ilcTH/UniCkMdtexkoCN0bI7pMcJDvmQFPvuPvmEaYA/NSfFTAgdUSLAoVjaRJm7+6PvcM+q1zYOwS4wTYMF9w=="],