feat(chat): Add image paste support

Paste images into the textarea to attach them to a message. Pending
images show as thumbnails above the input with a × remove button.
Images are sent to all three providers (OpenAI image_url, Anthropic
image_url via compat endpoint, Gemini inline_data).

chat/index.html

@@ -129,8 +129,14 @@
             .copy-btn:hover {
                 opacity: 1;
             }
-            .prompt {
+            .prompt-wrapper {
                 grid-area: prompt;
+                display: flex;
+                flex-direction: column;
+                gap: 0.5rem;
+                min-width: 0;
+            }
+            .prompt {
                 min-height: 40px;
                 padding: 0.8rem;
                 border: 1px solid var(--border-color);
@@ -272,7 +278,12 @@
                     <template x-for="(msg, idx) in visibleMessages" :key="idx">
                         <div :class="msg.role === 'user' ? 'message user-message' : 'message system-message'">
                             <template x-if="msg.role === 'user'">
+                                <div>
+                                    <template x-for="img in (msg.images || [])" :key="img.dataUrl">
+                                        <img :src="img.dataUrl" style="max-width: 100%; border-radius: 0.3rem; display: block; margin-bottom: 0.3rem;" />
+                                    </template>
                                     <div x-text="msg.content"></div>
+                                </div>
                             </template>
                             <template x-if="msg.role === 'assistant'">
                                 <div x-html="renderMarkdown(msg.content)"></div>
@@ -283,6 +294,15 @@
                 </div>
 
                 <!-- Textarea -->
+                <div class="prompt-wrapper">
+                    <div x-show="pendingImages.length > 0" style="display: flex; gap: 0.5rem; flex-wrap: wrap; align-items: flex-start;">
+                        <template x-for="(img, i) in pendingImages" :key="img.dataUrl">
+                            <div style="position: relative; display: inline-block;">
+                                <img :src="img.dataUrl" style="max-height: 72px; max-width: 120px; object-fit: cover; border-radius: 0.3rem; display: block;" />
+                                <button @click.prevent="pendingImages.splice(i, 1)" title="Remove" style="position: absolute; top: -0.35rem; right: -0.35rem; width: 1.1rem; height: 1.1rem; border-radius: 50%; background: #444; color: #fff; border: none; cursor: pointer; font-size: 0.65rem; line-height: 1; padding: 0; display: flex; align-items: center; justify-content: center;">&times;</button>
+                            </div>
+                        </template>
+                    </div>
                     <textarea
                         class="prompt"
                         placeholder="Type your message..."
@@ -291,7 +311,9 @@
                         :rows="inputRows"
                         @keydown.ctrl.enter="handleSubmit"
                         @keydown.meta.enter="handleSubmit"
+                        @paste="handlePaste"
                     ></textarea>
+                </div>
 
                 <!-- Action Button -->
                 <button class="submit" :class="isBusy && 'busy'" @click="isBusy ? abort() : handleSubmit()" x-text="isBusy ? 'Cancel' : 'Send'"></button>
@@ -326,7 +348,7 @@
         </div>
 
         <script defer src="./alpine@3.x.x.js"></script>
-        <script defer src="./markdown-it@14.1.0.min.js"></script>
+        <script src="./markdown-it@14.1.0.min.js"></script>
         <script>
             window.env ??= {};
             const systemPrompt = `
@@ -343,6 +365,7 @@
 
             const chatApp = () => ({
                 messages: [{ role: "system", content: systemPrompt }],
+                pendingImages: [],
                 promptText: window.env.PROMPT ? `${window.env.PROMPT}\n\n` : "",
                 activeModelName: "gemini-3-flash-preview",
                 historyItems: [],
@@ -403,9 +426,10 @@
                 renderMarkdown,
                 async handleSubmit() {
                     const text = this.promptText.trim();
-                    if (!text || this.isBusy) return;
+                    if ((!text && !this.pendingImages.length) || this.isBusy) return;
 
-                    this.messages.push({ role: "user", content: text });
+                    const images = this.pendingImages.splice(0);
+                    this.messages.push({ role: "user", content: text, images });
                     this.promptText = "";
                     this.isBusy = true;
                     this.abortController = new AbortController();
@@ -454,6 +478,21 @@
                     this.abortController?.abort();
                 },
 
+                handlePaste(e) {
+                    const items = [...(e.clipboardData?.items || [])];
+                    const imageItems = items.filter((item) => item.type.startsWith("image/"));
+                    if (!imageItems.length) return;
+                    e.preventDefault();
+                    imageItems.forEach((item) => {
+                        const reader = new FileReader();
+                        reader.onload = (ev) => {
+                            const dataUrl = ev.target.result;
+                            this.pendingImages.push({ dataUrl, base64: dataUrl.split(",")[1], mimeType: item.type });
+                        };
+                        reader.readAsDataURL(item.getAsFile());
+                    });
+                },
+
                 restoreConversation(msgs) {
                     this.messages = JSON.parse(JSON.stringify(msgs));
                     this.userHasScrolledUp = false;
@@ -485,7 +524,11 @@
                 const response = await fetch(`${baseUrl}/chat/completions`, {
                     method: "POST",
                     headers: { "Content-Type": "application/json", Authorization: `Bearer ${apiKey}`, ...extraHeaders },
-                    body: JSON.stringify({ model, messages, stream: true, ...rest }),
+                    body: JSON.stringify({ model, messages: messages.map(({ role, content, images }) =>
+                        images?.length
+                            ? { role, content: [{ type: "text", text: content }, ...images.map((img) => ({ type: "image_url", image_url: { url: img.dataUrl } }))] }
+                            : { role, content }
+                    ), stream: true, ...rest }),
                     signal,
                 });
                 if (!response.ok) {
@@ -540,6 +583,11 @@
                         parts = [...parts, ...fileParts];
                     }
 
+                    // Add pasted images
+                    if (role === "user" && msg.images?.length) {
+                        parts = [...parts, ...msg.images.map((img) => ({ inline_data: { mime_type: img.mimeType, data: img.base64 } }))];
+                    }
+
                     return {
                         role,
                         parts,