feat: multi-provider model configuration with UI/UX improvements (#355)

* feat: add multi-provider model configuration

- Add model config dialog for managing multiple AI providers
- Support for OpenAI, Anthropic, Google, Azure, Bedrock, OpenRouter, DeepSeek, SiliconFlow, Ollama, and AI Gateway
- Add model selector dropdown in chat panel header
- Add API key validation endpoint
- Add custom model ID input with keyboard navigation
- Fix hover highlight in Command component
- Add suggested models for each provider including latest Claude 4.5 series
- Store configuration locally in browser

* feat: improve model config UI and move selector to chat input

- Move model selector from header to chat input (left of send button)
- Add per-model validation status (queued, running, valid, invalid)
- Filter model selector to only show verified models
- Add editable model IDs in config dialog
- Add custom model input field alongside suggested models dropdown
- Fix hover states on provider buttons and select triggers
- Update OpenAI suggested models with GPT-5 series
- Add alert-dialog component for delete confirmation

* refactor: revert shadcn component changes, apply hover fix at usage site

* feat: add AWS credentials support for Bedrock provider

- Add AWS Access Key ID, Secret Access Key, Region fields for Bedrock
- Show different credential fields based on provider type
- Update validation API to handle Bedrock with AWS credentials
- Add region selector with common AWS regions

* fix: reset Test button after validation completes

* fix: reset validation button to Test after success

* fix: complete bedrock support and UI/UX improvements

- Add bedrock to ALLOWED_CLIENT_PROVIDERS for client credentials
- Pass AWS credentials through full chain (headers → API → provider)
- Replace non-existent GPT-5 models with real ones (o1, o3-mini)
- Add accessibility: aria-labels, focus-visible rings, inline errors
- Add more AWS regions (Ohio, London, Paris, Mumbai, Seoul, São Paulo)
- Fix setTimeout cleanup with useRef on component unmount
- Fix TypeScript type consistency in getSelectedAIConfig fallback

* chore: remove unused code

- Remove unused setAccessCodeRequired state in chat-panel.tsx
- Remove unused getSelectedModel export in model-config.ts

* fix: UI/UX improvements for model configuration dialog

- Add gradient header styling with icon badge
- Change Configuration section icon from Key to Settings2
- Add duplicate model detection with warning banner and inline removal
- Filter out already-added models from suggestions dropdown
- Add type-to-confirm for deleting providers with 3+ models
- Enhance delete confirmation dialog with warning icon
- Improve model selector discoverability (show model name + chevron)
- Add truncation for long model names with title tooltip
- Remove AI provider settings from Settings dialog (now in Model Config)
- Extract ValidationButton into reusable component

* fix: prevent duplicate model IDs within same provider

- Block adding model if ID already exists in provider
- Block editing model ID to match existing model in provider

* fix: improve duplicate model ID notifications

- Add toast notification when trying to add duplicate model
- Allow free typing when editing model ID, validate on blur
- Show warning toast instead of blocking input

* fix: improve duplicate model validation UX in config dialog

- Add inline error display for duplicate model IDs
- Show red border on input when error exists
- Validate on blur with shake animation for edit errors
- Prevent saving empty model names
- Clear errors when user starts typing
- Simplify error styling (small red text, no heavy chips)

components/chat-input.tsx

@@ -14,6 +14,7 @@ import { toast } from "sonner"
 import { ButtonWithTooltip } from "@/components/button-with-tooltip"
 import { ErrorToast } from "@/components/error-toast"
 import { HistoryDialog } from "@/components/history-dialog"
+import { ModelSelector } from "@/components/model-selector"
 import { ResetWarningModal } from "@/components/reset-warning-modal"
 import { SaveDialog } from "@/components/save-dialog"
 import { Button } from "@/components/ui/button"
@@ -28,6 +29,7 @@ import { useDiagram } from "@/contexts/diagram-context"
 import { useDictionary } from "@/hooks/use-dictionary"
 import { formatMessage } from "@/lib/i18n/utils"
 import { isPdfFile, isTextFile } from "@/lib/pdf-utils"
+import type { FlattenedModel } from "@/lib/types/model-config"
 import { FilePreviewList } from "./file-preview-list"
 
 const MAX_IMAGE_SIZE = 2 * 1024 * 1024 // 2MB
@@ -156,6 +158,11 @@ interface ChatInputProps {
     error?: Error | null
     minimalStyle?: boolean
     onMinimalStyleChange?: (value: boolean) => void
+    // Model selector props
+    models?: FlattenedModel[]
+    selectedModelId?: string
+    onModelSelect?: (modelId: string | undefined) => void
+    onConfigureModels?: () => void
 }
 
 export function ChatInput({
@@ -173,6 +180,10 @@ export function ChatInput({
     error = null,
     minimalStyle = false,
     onMinimalStyleChange = () => {},
+    models = [],
+    selectedModelId,
+    onModelSelect = () => {},
+    onConfigureModels = () => {},
 }: ChatInputProps) {
     const dict = useDictionary()
     const {
@@ -465,6 +476,14 @@ export function ChatInput({
                             disabled={isDisabled}
                         />
 
+                        <ModelSelector
+                            models={models}
+                            selectedModelId={selectedModelId}
+                            onSelect={onModelSelect}
+                            onConfigure={onConfigureModels}
+                            disabled={isDisabled}
+                        />
+
                         <div className="w-px h-5 bg-border mx-1" />
 
                         <Button