feat(generate): add rust support to mise toolchain settings and build plan

Generated-by: aiautocommit

Author: iloveitaly

core/__snapshots__/TestGenerateBuildPlanForExamples_rust-custom-toolchain_1.snap.json

@@ -43,6 +43,10 @@
     {
      "path": "/mise/shims"
     },
+    {
+     "dest": "rust-toolchain.toml",
+     "src": "rust-toolchain.toml"
+    },
     {
      "customName": "create mise config",
      "name": "generated-mise-toml",

core/generate/__snapshots__/context_test.snap

@@ -22,7 +22,7 @@
  "steps": [
   {
    "assets": {
-    "generated-mise-toml": "[tools]\n  go = \"1.23.5\"\n  node = \"20.18.2\"\n  python = \"3.13.1\"\n\n[settings]\n  idiomatic_version_file_enable_tools = [\"python\", \"node\", \"ruby\", \"elixir\", \"go\", \"java\", \"yarn\", \"bun\", \"deno\"]\n  minimum_release_age = \"14d\"\n  paranoid = true\n  trusted_config_paths = [\"/app\"]\n  [settings.node]\n    verify = false\n"
+    "generated-mise-toml": "[tools]\n  go = \"1.23.5\"\n  node = \"20.18.2\"\n  python = \"3.13.1\"\n\n[settings]\n  idiomatic_version_file_enable_tools = [\"python\", \"node\", \"ruby\", \"elixir\", \"go\", \"java\", \"yarn\", \"bun\", \"deno\", \"rust\"]\n  minimum_release_age = \"14d\"\n  paranoid = true\n  trusted_config_paths = [\"/app\"]\n  [settings.node]\n    verify = false\n"
    },
    "commands": [
     {