fix(translator): sanitize tool names for Gemini function_declarations compatibility

Claude Code and MCP clients may send tool names containing characters
invalid for Gemini's function_declarations (e.g. '/', '@', spaces).
Sanitize on request via SanitizeFunctionName and restore original names
on response for both antigravity/claude and gemini-cli/claude translators.

internal/translator/antigravity/claude/antigravity_claude_response.go

@@ -44,6 +44,10 @@ type Params struct {
 
 	// Signature caching support
 	CurrentThinkingText strings.Builder // Accumulates thinking text for signature caching
+
+	// Reverse map: sanitized Gemini function name → original Claude tool name.
+	// Populated lazily on the first response chunk from the original request JSON.
+	ToolNameMap map[string]string
 }
 
 // toolUseIDCounter provides a process-wide unique counter for tool use identifiers.
@@ -77,6 +81,10 @@ func ConvertAntigravityResponseToClaude(_ context.Context, _ string, originalReq
 
 	params := (*param).(*Params)
 
+	if params.ToolNameMap == nil {
+		params.ToolNameMap = util.SanitizedToolNameMap(originalRequestRawJSON)
+	}
+
 	if bytes.Equal(rawJSON, []byte("[DONE]")) {
 		output := make([]byte, 0, 256)
 		// Only send final events if we have actually output content
@@ -212,7 +220,7 @@ func ConvertAntigravityResponseToClaude(_ context.Context, _ string, originalReq
 				// Handle function/tool calls from the AI model
 				// This processes tool usage requests and formats them for Claude Code API compatibility
 				params.HasToolUse = true
-				fcName := functionCallResult.Get("name").String()
+				fcName := util.RestoreSanitizedToolName(params.ToolNameMap, functionCallResult.Get("name").String())
 
 				// Handle state transitions when switching to function calls
 				// Close any existing function call block first
@@ -348,7 +356,7 @@ func resolveStopReason(params *Params) string {
 // Returns:
 //   - []byte: A Claude-compatible JSON response.
 func ConvertAntigravityResponseToClaudeNonStream(_ context.Context, _ string, originalRequestRawJSON, requestRawJSON, rawJSON []byte, _ *any) []byte {
-	_ = originalRequestRawJSON
+	toolNameMap := util.SanitizedToolNameMap(originalRequestRawJSON)
 	modelName := gjson.GetBytes(requestRawJSON, "model").String()
 
 	root := gjson.ParseBytes(rawJSON)
@@ -450,7 +458,7 @@ func ConvertAntigravityResponseToClaudeNonStream(_ context.Context, _ string, or
 				flushText()
 				hasToolCall = true
 
-				name := functionCall.Get("name").String()
+				name := util.RestoreSanitizedToolName(toolNameMap, functionCall.Get("name").String())
 				toolIDCounter++
 				toolBlock := []byte(`{"type":"tool_use","id":"","name":"","input":{}}`)
 				toolBlock, _ = sjson.SetBytes(toolBlock, "id", fmt.Sprintf("tool_%d", toolIDCounter))