feat: golem15.golem plugin with the OpenAI-compatible adapter and AIService.Send

- Prompt, Payload and AIResponse value objects ported from Golem15.Golem
- OpenAIAdapter: chat completions mapping with PHP's response_format,
  max_completion_tokens and reasoning_effort rules
- AIService.Send through fetchguard (TrustedMode for operator models,
  PublicOnlyMode otherwise) with PHP's failure messages
- config defaults for the SSRF allowlist and the AI timeout, lang, README

classes/valueobjects/response.go

@@ -0,0 +1,56 @@
+package valueobjects
+
+// AIResponse is the outcome of an AI call. A success carries Content,
+// Usage and the provider's decoded answer in Raw; a failure carries Error,
+// PHP's message for the caller, and sometimes Raw (the provider's error
+// body, or {"raw": body} when the answer was not JSON). Err is the Go
+// error behind a failure, for logs and tests; it is never shown to a user
+// and may be nil.
+type AIResponse struct {
+	Success bool
+	Content string
+	Error   string
+	Usage   map[string]any
+	Raw     map[string]any
+	Err     error
+}
+
+// Success builds a successful response.
+func Success(content string, usage, raw map[string]any) AIResponse {
+	if usage == nil {
+		usage = map[string]any{}
+	}
+	if raw == nil {
+		raw = map[string]any{}
+	}
+	return AIResponse{Success: true, Content: content, Usage: usage, Raw: raw}
+}
+
+// Failure builds a failed response.
+func Failure(message string, raw map[string]any) AIResponse {
+	if raw == nil {
+		raw = map[string]any{}
+	}
+	return AIResponse{Error: message, Usage: map[string]any{}, Raw: raw}
+}
+
+// TotalTokens is usage.total_tokens, 0 when absent.
+func (r AIResponse) TotalTokens() int { return usageInt(r.Usage, "total_tokens") }
+
+// PromptTokens is usage.prompt_tokens, 0 when absent.
+func (r AIResponse) PromptTokens() int { return usageInt(r.Usage, "prompt_tokens") }
+
+// CompletionTokens is usage.completion_tokens, 0 when absent.
+func (r AIResponse) CompletionTokens() int { return usageInt(r.Usage, "completion_tokens") }
+
+func usageInt(m map[string]any, k string) int {
+	switch n := m[k].(type) {
+	case int:
+		return n
+	case int64:
+		return int(n)
+	case float64:
+		return int(n)
+	}
+	return 0
+}