Add image support in tool results across all providers

Tool results now use content blocks and can include both text and images.
All providers (Anthropic, Google, OpenAI Completions, OpenAI Responses)
correctly pass images from tool results to LLMs.

- Update ToolResultMessage type to use content blocks
- Add placeholder text for image-only tool results in Google/Anthropic
- OpenAI providers send tool result + follow-up user message with images
- Fix Anthropic JSON parsing for empty tool arguments
- Add comprehensive tests for image-only and text+image tool results
- Update README with tool result content blocks API

packages/web-ui/src/tools/renderers/BashRenderer.ts

@@ -16,7 +16,11 @@ export class BashRenderer implements ToolRenderer<BashParams, undefined> {
 
 		// With result: show command + output
 		if (result && params?.command) {
-			const output = result.output || "";
+			const output =
+				result.content
+					?.filter((c) => c.type === "text")
+					.map((c: any) => c.text)
+					.join("\n") || "";
 			const combined = output ? `> ${params.command}\n\n${output}` : `> ${params.command}`;
 			return {
 				content: html`

packages/web-ui/src/tools/renderers/CalculateRenderer.ts

@@ -16,7 +16,11 @@ export class CalculateRenderer implements ToolRenderer<CalculateParams, undefine
 
 		// Full params + full result
 		if (result && params?.expression) {
-			const output = result.output || "";
+			const output =
+				result.content
+					?.filter((c) => c.type === "text")
+					.map((c: any) => c.text)
+					.join("\n") || "";
 
 			// Error: show expression in header, error below
 			if (result.isError) {

packages/web-ui/src/tools/renderers/DefaultRenderer.ts

@@ -25,7 +25,11 @@ export class DefaultRenderer implements ToolRenderer {
 
 		// With result: show header + params + result
 		if (result) {
-			let outputJson = result.output || i18n("(no output)");
+			let outputJson =
+				result.content
+					?.filter((c) => c.type === "text")
+					.map((c: any) => c.text)
+					.join("\n") || i18n("(no output)");
 			let outputLanguage = "text";
 
 			// Try to parse and pretty-print if it's valid JSON

packages/web-ui/src/tools/renderers/GetCurrentTimeRenderer.ts

@@ -19,7 +19,11 @@ export class GetCurrentTimeRenderer implements ToolRenderer<GetCurrentTimeParams
 
 		// Full params + full result
 		if (result && params) {
-			const output = result.output || "";
+			const output =
+				result.content
+					?.filter((c) => c.type === "text")
+					.map((c: any) => c.text)
+					.join("\n") || "";
 			const headerText = params.timezone
 				? `${i18n("Getting current time in")} ${params.timezone}`
 				: i18n("Getting current date and time");
@@ -43,7 +47,11 @@ export class GetCurrentTimeRenderer implements ToolRenderer<GetCurrentTimeParams
 
 		// Full result, no params
 		if (result) {
-			const output = result.output || "";
+			const output =
+				result.content
+					?.filter((c) => c.type === "text")
+					.map((c: any) => c.text)
+					.join("\n") || "";
 
 			// Error: show header, error below
 			if (result.isError) {