fix(error-interception): show errors to user in UI alongside AI guidance

Add cline.say('error') calls to 3 bypass paths in presentAssistantMessage.ts
where intercepted errors were sent only to the AI model but never shown to
the user in the Zoo Code chat UI:

- Structural preflight path (CWD_OBJECT_MISUSE, NESTED_PARAM_OVERFLOW)
- Validation catch path (modeRestriction, unknownTool, fileRestriction)
- Missing nativeArgs path (PARAM_MISSING, INVALID_JSON_ARGUMENTS)

This ensures both user visibility AND AI guidance happen simultaneously,
matching the core design principle: errors must never be hidden from users.

Author: Zoo (VP)

src/core/assistant-message/__tests__/presentAssistantMessage-error-interception.spec.ts

@@ -252,6 +252,10 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 				"execute_command",
 				expect.stringContaining("CWD_OBJECT_MISUSE"),
 			)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
+			expect(errorSayCalls[0][1]).toContain("CWD_OBJECT_MISUSE")
 		})
 
 		it("blocks tool_use with NESTED_PARAM_OVERFLOW and pushes guided tool_result", async () => {
@@ -286,6 +290,10 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 				"read_file",
 				expect.stringContaining("NESTED_PARAM_OVERFLOW"),
 			)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
+			expect(errorSayCalls[0][1]).toContain("NESTED_PARAM_OVERFLOW")
 		})
 
 		it("escalates to STRUCTURAL_MISUSE_REPEAT on second identical misuse", async () => {
@@ -402,6 +410,9 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 				expect.stringContaining("missing nativeArgs"),
 			)
 			expect(mockTask.didAlreadyUseTool).toBe(false)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
 		})
 	})
 
@@ -500,6 +511,7 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 					id: toolCallId,
 					name: "read_file",
 					params: { path: "x.txt" },
+					nativeArgs: { path: "x.txt" },
 					partial: false,
 				},
 			]
@@ -513,6 +525,10 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 			expect(toolResult.is_error).toBe(true)
 			expect(mockTask.consecutiveMistakeCount).toBe(1)
 			expect(mockTask.didAlreadyUseTool).toBe(false)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
+			expect(errorSayCalls[0][1]).toContain("not allowed in")
 		})
 
 		it("classifies 'Unknown tool' as unknownTool and pushes tool_result", async () => {
@@ -528,6 +544,7 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 					id: toolCallId,
 					name: "fake_tool_xyz",
 					params: {},
+					nativeArgs: {},
 					partial: false,
 				},
 			]
@@ -540,6 +557,10 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 			expect(toolResult).toBeDefined()
 			expect(toolResult.is_error).toBe(true)
 			expect(mockTask.consecutiveMistakeCount).toBe(1)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
+			expect(errorSayCalls[0][1]).toContain("Unknown tool")
 		})
 
 		it("classifies 'File restriction' as fileRestriction and pushes tool_result", async () => {
@@ -555,6 +576,7 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 					id: toolCallId,
 					name: "write_to_file",
 					params: { path: ".git/config", content: "bad" },
+					nativeArgs: { path: ".git/config", content: "bad" },
 					partial: false,
 				},
 			]
@@ -566,6 +588,10 @@ describe("presentAssistantMessage - Error Interception Integration", () => {
 			)
 			expect(toolResult).toBeDefined()
 			expect(toolResult.is_error).toBe(true)
+			// User must see the error in the UI (design principle: both must happen).
+			const errorSayCalls = mockTask.say.mock.calls.filter((c: any[]) => c[0] === "error")
+			expect(errorSayCalls.length).toBe(1)
+			expect(errorSayCalls[0][1]).toContain("File restriction")
 		})
 	})
 

src/core/assistant-message/presentAssistantMessage.ts

@@ -553,6 +553,10 @@ export async function presentAssistantMessage(cline: Task) {
 					// continue gracefully.
 					const missingArgsGuide = getTaskErrorState(cline).consumePendingNativeProtocolGuide()
 					const missingArgsBase = guided ?? formatResponse.toolError(errorMessage)
+					// Show the invalid/missing args error to the user in the UI chat.
+					// The AI receives the guided payload below; the user must also
+					// see what went wrong (design principle: both must happen).
+					await cline.say("error", `Invalid tool call: ${errorMessage}`)
 					cline.pushToolResultToUserContent({
 						type: "tool_result",
 						tool_use_id: sanitizeToolUseId(toolCallId),
@@ -770,6 +774,10 @@ export async function presentAssistantMessage(cline: Task) {
 
 					const structuralGuide = taskErrorState.consumePendingNativeProtocolGuide()
 					const structuralBase = guided ?? formatResponse.toolError(errorMessage)
+					// Show the structural error to the user in the UI chat.
+					// The AI receives the guided payload below; the user must also
+					// see what went wrong (design principle: both must happen).
+					await cline.say("error", `[${variant}] ${errorMessage}`)
 					cline.pushToolResultToUserContent({
 						type: "tool_result",
 						tool_use_id: sanitizeToolUseId(toolCallId),
@@ -845,6 +853,10 @@ export async function presentAssistantMessage(cline: Task) {
 					// Push tool_result directly without setting didAlreadyUseTool
 					const validationGuide = getTaskErrorState(cline).consumePendingNativeProtocolGuide()
 					const validationBase = guided ? `${guided}\n\n${errorMessage}` : errorMessage
+					// Show the validation error to the user in the UI chat.
+					// The AI receives the guided payload below; the user must also
+					// see what went wrong (design principle: both must happen).
+					await cline.say("error", `Validation error: ${errorMessage}`)
 					cline.pushToolResultToUserContent({
 						type: "tool_result",
 						tool_use_id: sanitizeToolUseId(toolCallId),