fix: sanitize tool_use.id to comply with Claude API regex ^[a-zA-Z0-9_-]+$

Add util.SanitizeClaudeToolID() to replace non-conforming characters in
tool_use.id fields across all five response translators (gemini, codex,
openai, antigravity, gemini-cli).

Upstream tool names may contain dots or other special characters
(e.g. "fs.readFile") that violate Claude's ID validation regex.
The sanitizer replaces such characters with underscores and provides
a generated fallback for empty IDs.

Fixes #1872, Fixes #1849

Made-with: Cursor

internal/util/claude_tool_id.go

@@ -0,0 +1,24 @@
+package util
+
+import (
+	"fmt"
+	"regexp"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	claudeToolUseIDSanitizer = regexp.MustCompile(`[^a-zA-Z0-9_-]`)
+	claudeToolUseIDCounter   uint64
+)
+
+// SanitizeClaudeToolID ensures the given id conforms to Claude's
+// tool_use.id regex ^[a-zA-Z0-9_-]+$.  Non-conforming characters are
+// replaced with '_'; an empty result gets a generated fallback.
+func SanitizeClaudeToolID(id string) string {
+	s := claudeToolUseIDSanitizer.ReplaceAllString(id, "_")
+	if s == "" {
+		s = fmt.Sprintf("toolu_%d_%d", time.Now().UnixNano(), atomic.AddUint64(&claudeToolUseIDCounter, 1))
+	}
+	return s
+}