feat(vision): consult_vision tool + vision settings API

Backend vision update (additive to [email protected] / [email protected],
no version bump).

Contracts mirrored (.dispatch/transport-contract.reference.md):
- VisionSettingsResponse + SetVisionSettingsRequest (GET/PUT /settings/vision).
- Delta note: read_image -> consult_vision; numbered placeholders; compaction.

Tool rendering (ChatView):
- read_image test -> consult_vision (rendering is generic by toolName).
- +2 tests: numbered-placeholder text chunk + [Compacted image] text chunk
  (both regular text chunks, render as-is — no special handling).

New vision feature library (src/features/vision/):
- logic/view-model.ts (32 tests): VisionSettings/VisionSettingsPatch types
  (consumer-defines-port), LoadVisionSettings/SaveVisionSettings ports +
  results, normalizeVisionSettings (network-seam coercion), parseImageLimit/
  imageLimitChanged, compactionModelOptions (vision-capable models via chat's
  public isVisionModel + Auto sentinel), round-trip helpers, imageLimitLabel.
- ui/VisionSettingsView.svelte (9 tests): imageLimit input + Save,
  compactionModel dropdown (Auto + vision-capable models), load-on-mount,
  save-on-change, error/saved feedback.
- index.ts.

Cross-unit seam: isVisionModel added to features/chat public index.ts
(additive); imported through the public surface, not internals.

Store wiring (src/app/store.svelte.ts):
- visionSettings state + refreshVisionSettings (GET /settings/vision,
  normalized at the seam) + setVisionSettings (PUT, partial, returns merged) +
  VisionSettingsResult; seeded on boot; exposed on AppStore. +4 store tests.

Mounted in App.svelte: new "Vision" sidebar view kind + VisionSettingsView
in viewContent (not conversation-scoped); load/save adapters; visionManifest.

Verification: svelte-check 0/0; vitest 948/948 (run twice, +47 since the
prior vision commit); biome clean; vite build OK. See backend-handoff.md §2j.

Not merged or pushed.

1 files changed, 38 insertions, 0 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index f240a06..f41d7ba 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -77,6 +77,13 @@
 		type SaveSystemPrompt as SaveSystemPromptAlias,
 		manifest as systemPromptManifest,
 	} from "../features/system-prompt";
+	import {
+		VisionSettingsView,
+		manifest as visionManifest,
+		type LoadVisionSettingsResult,
+		type SaveVisionSettingsResult,
+		type VisionSettingsPatch,
+	} from "../features/vision";
 	import type { AppStore } from "./store.svelte";
 	import ErrorModal from "./ErrorModal.svelte";
 	import { createLocalStore } from "../adapters/local-storage";
@@ -106,6 +113,7 @@
 		{ id: "cache-warming", label: "Cache Warming" },
 		{ id: "tasks", label: "Tasks" },
 		{ id: "compaction", label: "Compaction" },
+		{ id: "vision", label: "Vision" },
 		{ id: "heartbeat", label: "Heartbeat" },
 		{ id: "system-prompt", label: "System Prompt" },
 		{ id: "settings", label: "Settings" },
@@ -143,6 +151,7 @@
 		settingsManifest,
 		systemPromptManifest,
 		heartbeatManifest,
+		visionManifest,
 	].map((m) => [m.name, m.description] as const);
 
 	// Smart-scroll: keep the transcript pinned to the bottom while it streams,
@@ -304,6 +313,27 @@
 			: { ok: false, error: result.error };
 	}
 
+	// Adapt the store's global vision-settings API to the vision feature's ports.
+	async function loadVisionSettings(): Promise<LoadVisionSettingsResult> {
+		// The store seeds `visionSettings` on boot; a refresh keeps it current.
+		await store.refreshVisionSettings();
+		const settings = store.visionSettings;
+		if (settings === null) {
+			return { ok: false, error: "Vision settings not available." };
+		}
+		return { ok: true, settings };
+	}
+
+	async function saveVisionSettings(
+		patch: VisionSettingsPatch,
+	): Promise<SaveVisionSettingsResult> {
+		const result = await store.setVisionSettings(patch);
+		if (result === null) return { ok: false, error: "Vision settings not available." };
+		return result.ok
+			? { ok: true, settings: result.settings }
+			: { ok: false, error: result.error };
+	}
+
 	// Adapt the store's chat-limit result to the settings feature's port. On a
 	// raise the active chat refills (prepends older history); preserve the
 	// reader's viewport over the prepend (the manual analogue of CSS scroll
@@ -660,6 +690,14 @@
 				savePercent={saveCompactPercent}
 			/>
 		{/key}
+	{:else if kind === "vision"}
+		<!-- Global vision settings (image compaction). Not conversation-scoped (no {#key}). -->
+		<VisionSettingsView
+			models={store.models}
+			modelInfo={store.modelInfo}
+			load={loadVisionSettings}
+			save={saveVisionSettings}
+		/>
 	{:else if kind === "system-prompt"}
 		<!-- Global system prompt template. Opens a full-page modal editor (half
 		     template / half variable palette). Not conversation-scoped (no {#key}). -->