feat(vision): image paste + transcript image rendering + vision badge

Vision & vision-handoff frontend (consumes the backend's additive
[email protected] / [email protected] image types — no version bump).

Contracts mirrored:
- .dispatch/wire.reference.md: ImageChunk added to the Chunk union +
  ImageChunk/ImageInput interfaces.
- .dispatch/transport-contract.reference.md: ChatRequest.images,
  ModelMetadata.vision, + ImageChunk/ImageInput re-exports.

Core (core/chunks):
- conformance: assertChunkExhaustive handles the new 'image' variant
  (the guard caught it — its purpose).
- appendUserMessage(state, text, images?) echoes a [text, image, ...]
  user run; the user-message event dedup scans the trailing user run
  (not just the last chunk) so an image-bearing echo doesn't duplicate
  the text; applyHistory's during-gen dedup matches a multi-chunk echo
  by content equality (chunkContentEquals + trailingRun helpers).

UI:
- ChatView renders user 'image' chunks as lazy <img> bubbles; a
  non-vision model's persisted [image, analysis-text] both render.
  read_image tool renders generically (no special-casing).
- Composer: clipboard paste / file picker / drag-drop of images ->
  base64 data URLs, thumbnail previews with remove, forwarded on
  chat.send (omitted when none). Image-only sends allowed; steering
  (chat.queue) never forwards images.
- ModelSelector: vision badge (isVisionModel) marks vision-capable
  models; indicator shows native-vision vs vision-handoff hint.

Store wiring: ChatStore.send + AppStore.send + App.svelte handleSend
thread images through; chat.send still omits cwd (only images added).

Verification: svelte-check 0/0; vitest 901/901 (run twice, +34 new);
biome clean; vite build OK. See backend-handoff.md §2j.

Not merged or pushed.

1 files changed, 32 insertions, 1 deletions

diff --git a/src/features/chat/model-select.test.ts b/src/features/chat/model-select.test.ts
index deb673d..6d3081d 100644
--- a/src/features/chat/model-select.test.ts
+++ b/src/features/chat/model-select.test.ts
@@ -1,5 +1,11 @@
 import { describe, expect, it } from "vitest";
-import { joinModelName, modelKeys, modelsForKey, splitModelName } from "./model-select";
+import {
+  isVisionModel,
+  joinModelName,
+  modelKeys,
+  modelsForKey,
+  splitModelName,
+} from "./model-select";
 
 describe("splitModelName", () => {
   it("splits on the first slash", () => {
@@ -56,3 +62,28 @@ describe("modelsForKey", () => {
     expect(modelsForKey(["openai/gpt-4"], "anthropic")).toEqual([]);
   });
 });
+
+describe("isVisionModel", () => {
+  it("returns true when modelInfo[name].vision is true", () => {
+    const info = { "kimi/k2": { vision: true } };
+    expect(isVisionModel(info, "kimi/k2")).toBe(true);
+  });
+
+  it("returns false when vision is false", () => {
+    const info = { "umans/glm-5.2": { vision: false } };
+    expect(isVisionModel(info, "umans/glm-5.2")).toBe(false);
+  });
+
+  it("returns false when vision is absent (unknown)", () => {
+    const info = { "umans/glm-5.2": { contextWindow: 128000 } };
+    expect(isVisionModel(info, "umans/glm-5.2")).toBe(false);
+  });
+
+  it("returns false for a model with no metadata entry at all", () => {
+    expect(isVisionModel({}, "unknown/model")).toBe(false);
+  });
+
+  it("returns false for an empty modelInfo map", () => {
+    expect(isVisionModel({}, "kimi/k2")).toBe(false);
+  });
+});