fix(look-at): use direct file passthrough instead of Read tool (#173)

- Embed files directly in message parts using file:// URL format
- Remove dependency on Read tool for multimodal-looker agent
- Add inferMimeType helper for proper MIME type detection
- Disable read tool in agent tools config (no longer needed)
- Upgrade multimodal-looker model to gemini-3-flash
- Update all README docs to reflect gemini-3-flash change

Fixes #126

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/agents/multimodal-looker.ts

@@ -4,7 +4,7 @@ export const multimodalLookerAgent: AgentConfig = {
   description:
     "Analyze media files (PDFs, images, diagrams) that require interpretation beyond raw text. Extracts specific information or summaries from documents, describes visual content. Use when you need analyzed/extracted data rather than literal file contents.",
   mode: "subagent",
-  model: "google/gemini-2.5-flash",
+  model: "google/gemini-3-flash",
   temperature: 0.1,
   tools: { write: false, edit: false, bash: false, background_task: false },
   prompt: `You interpret media files that cannot be read as plain text.

src/tools/look-at/tools.ts

@@ -1,8 +1,33 @@
+import { extname, basename } from "node:path"
 import { tool, type PluginInput } from "@opencode-ai/plugin"
 import { LOOK_AT_DESCRIPTION, MULTIMODAL_LOOKER_AGENT } from "./constants"
 import type { LookAtArgs } from "./types"
 import { log } from "../../shared/logger"
 
+function inferMimeType(filePath: string): string {
+  const ext = extname(filePath).toLowerCase()
+  const mimeTypes: Record<string, string> = {
+    ".jpg": "image/jpeg",
+    ".jpeg": "image/jpeg",
+    ".png": "image/png",
+    ".gif": "image/gif",
+    ".webp": "image/webp",
+    ".svg": "image/svg+xml",
+    ".bmp": "image/bmp",
+    ".ico": "image/x-icon",
+    ".pdf": "application/pdf",
+    ".txt": "text/plain",
+    ".md": "text/markdown",
+    ".json": "application/json",
+    ".xml": "application/xml",
+    ".html": "text/html",
+    ".css": "text/css",
+    ".js": "text/javascript",
+    ".ts": "text/typescript",
+  }
+  return mimeTypes[ext] || "application/octet-stream"
+}
+
 export function createLookAt(ctx: PluginInput) {
   return tool({
     description: LOOK_AT_DESCRIPTION,
@@ -13,12 +38,14 @@ export function createLookAt(ctx: PluginInput) {
     async execute(args: LookAtArgs, toolContext) {
       log(`[look_at] Analyzing file: ${args.file_path}, goal: ${args.goal}`)
 
+      const mimeType = inferMimeType(args.file_path)
+      const filename = basename(args.file_path)
+
       const prompt = `Analyze this file and extract the requested information.
 
-File path: ${args.file_path}
 Goal: ${args.goal}
 
-Read the file using the Read tool, then provide ONLY the extracted information that matches the goal.
+Provide ONLY the extracted information that matches the goal.
 Be thorough on what was requested, concise on everything else.
 If the requested information is not found, clearly state what is missing.`
 
@@ -38,7 +65,7 @@ If the requested information is not found, clearly state what is missing.`
       const sessionID = createResult.data.id
       log(`[look_at] Created session: ${sessionID}`)
 
-      log(`[look_at] Sending prompt to session ${sessionID}`)
+      log(`[look_at] Sending prompt with file passthrough to session ${sessionID}`)
       await ctx.client.session.prompt({
         path: { id: sessionID },
         body: {
@@ -47,8 +74,12 @@ If the requested information is not found, clearly state what is missing.`
             task: false,
             call_omo_agent: false,
             look_at: false,
+            read: false,
           },
-          parts: [{ type: "text", text: prompt }],
+          parts: [
+            { type: "text", text: prompt },
+            { type: "file", mime: mimeType, url: `file://${args.file_path}`, filename },
+          ],
         },
       })