style: UI polish and miscellaneous fixes

Fixes link color from hardcoded white to currentColor for proper theme
support. Adds video and audio modality icons to ModelInfo. Registers
anthropic, nvidia, and xiaomi in the provider icon map. Removes unused
pagination validation from agents and topics endpoints. Adds convenience
start script. Updates AGENTS.md.

app/components/ModelSelector.vue

@@ -1,6 +1,7 @@
 <script setup lang="ts">
 import { ref, computed, watch, nextTick } from 'vue';
 import { useFloating, offset, flip, shift, autoUpdate, size, hide } from '@floating-ui/vue';
+import type { DialogType } from '~/composables/useDialog';
 import type { Model, ModelWithProvider, Provider, ProviderWithModels } from '~/composables/useModels';
 import { sortByReleaseDate } from '~/utils/sort';
 import RowVirtualizerFixed from './RowVirtualizerFixed.vue';
@@ -211,7 +212,7 @@ onUnmounted(() => {
 
 <template>
     <div role="button" @click="toggleDropdown()" ref="dropdownButton"
-        class="cursor-pointer flex items-center min-w-0 select-none gap-2 px-3 py-1.5 rounded-lg text-sm font-medium transition-colors duration-200"
+        class="cursor-pointer flex items-center w-fit min-w-0 select-none gap-2 px-3 py-1.5 rounded-lg text-sm font-medium transition-colors duration-200"
         :class="[
             isOpen
                 ? 'bg-[var(--color-hover)] text-[var(--text-primary)]'