ui: finish shadcn migration and remove legacy shim

Convert the remaining .btn usages (Concurrency, Performance, CaptureDialog)
to shadcn Button, fix CaptureDialog/PerformanceChart styles to shadcn
tokens, and remove the transitional legacy palette aliases and component
classes from index.css. Drop the now-unused lucide-svelte and shadcn-svelte
dependencies.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UmuGqwNBJNEAMaWsdCDqUC

ui-svelte/package-lock.json

@@ -11,7 +11,6 @@
         "chart.js": "4.5.1",
         "highlight.js": "^11.11.1",
         "katex": "^0.16.28",
-        "lucide-svelte": "^0.563.0",
         "rehype-katex": "^7.0.1",
         "rehype-stringify": "^10.0.1",
         "remark-gfm": "^4.0.1",
@@ -33,7 +32,6 @@
         "bits-ui": "^2.18.1",
         "clsx": "^2.1.1",
         "paneforge": "^1.0.2",
-        "shadcn-svelte": "^1.3.0",
         "svelte": "^5.46.4",
         "svelte-check": "^4.1.4",
         "tailwind-merge": "^3.6.0",
@@ -1980,15 +1978,6 @@
         "url": "https://github.com/sponsors/wooorm"
       }
     },
-    "node_modules/lucide-svelte": {
-      "version": "0.563.0",
-      "resolved": "https://registry.npmjs.org/lucide-svelte/-/lucide-svelte-0.563.0.tgz",
-      "integrity": "sha512-pjZKw7TpQcamfQrx7YdbOHgmrcNeKiGGMD0tKZQaVktwSsbqw28CsKc2Q97ttwjytiCWkJyOa8ij2Q+Og0nPfQ==",
-      "license": "ISC",
-      "peerDependencies": {
-        "svelte": "^3 || ^4 || ^5.0.0-next.42"
-      }
-    },
     "node_modules/lz-string": {
       "version": "1.5.0",
       "resolved": "https://registry.npmjs.org/lz-string/-/lz-string-1.5.0.tgz",
@@ -2865,13 +2854,6 @@
         "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
       }
     },
-    "node_modules/node-fetch-native": {
-      "version": "1.6.7",
-      "resolved": "https://registry.npmjs.org/node-fetch-native/-/node-fetch-native-1.6.7.tgz",
-      "integrity": "sha512-g9yhqoedzIUm0nTnTqAQvueMPVOuIY16bqgAJJC8XOOubYFNwz6IER9qs0Gq2Xd0+CecCKFjtdDTMA4u4xG06Q==",
-      "dev": true,
-      "license": "MIT"
-    },
     "node_modules/obug": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/obug/-/obug-2.1.1.tgz",
@@ -3240,35 +3222,6 @@
         "node": ">=6"
       }
     },
-    "node_modules/shadcn-svelte": {
-      "version": "1.3.0",
-      "resolved": "https://registry.npmjs.org/shadcn-svelte/-/shadcn-svelte-1.3.0.tgz",
-      "integrity": "sha512-Pd4ICWTkTks/b2YU4c9vF2XsX1x5HFPRl5bKszS1LcnWS83x+7T4WiIvbWz8Qh9knkcGZ+SCz1+Dmhdq+AYooA==",
-      "dev": true,
-      "license": "MIT",
-      "dependencies": {
-        "commander": "^14.0.0",
-        "node-fetch-native": "^1.6.4",
-        "postcss": "^8.5.5",
-        "tailwind-merge": "^3.0.0"
-      },
-      "bin": {
-        "shadcn-svelte": "dist/index.mjs"
-      },
-      "peerDependencies": {
-        "svelte": "^5.0.0"
-      }
-    },
-    "node_modules/shadcn-svelte/node_modules/commander": {
-      "version": "14.0.3",
-      "resolved": "https://registry.npmjs.org/commander/-/commander-14.0.3.tgz",
-      "integrity": "sha512-H+y0Jo/T1RZ9qPP4Eh1pkcQcLRglraJaSLoyOtHxu6AapkjWVCy2Sit1QQ4x3Dng8qDlSsZEet7g5Pq06MvTgw==",
-      "dev": true,
-      "license": "MIT",
-      "engines": {
-        "node": ">=20"
-      }
-    },
     "node_modules/siginfo": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/siginfo/-/siginfo-2.0.0.tgz",