revert(qoder): drop the Responses usage plumbing from shared code

The merged Qoder work also rewrote shared translator/handler code so that
/v1/responses clients got token usage on response.completed. That changed
behaviour for every provider, not just Qoder: proxies saw input tokens
rise by the 2000-token context buffer, and the plain token mapping was
replaced by one that always adds input_tokens_details.

A probe confirms the Qoder benefit does not depend on those edits: the
executor's coalescer already emits one include_usage-style finish chunk, so
a Claude client receives input_tokens and cache_read_input_tokens with
every shared file at its original state. Only the Responses path relies on
the shared translator, and that path has no Qoder-owned seam to put it in.

Reverts the shared files to their pre-PR state and drops the Responses
usage test. The Cline envelope unwrap in nonStreamingHandler.js, which
landed after the PR in the same file, is kept.

open-sse/handlers/chatCore/nonStreamingHandler.js

@@ -11,7 +11,6 @@ import { buildRequestDetail, extractRequestConfig, extractUsageFromResponse, sav
 import { appendRequestLog, saveRequestDetail } from "@/lib/usageDb.js";
 import { decloakToolNames } from "../../utils/claudeCloaking.js";
 import { ROLE, RESPONSES_ITEM } from "../../translator/schema/index.js";
-import { toResponsesUsage } from "../../translator/concerns/usage.js";
 
 function parseToolArguments(value) {
   if (!value) return {};
@@ -132,8 +131,11 @@ function openAICompletionToResponses(responseBody, customToolNames = null) {
     background: false,
     error: null,
     output,
-    // Keep cached/reasoning details (input_tokens_details) — proxies bill cache hits from them
-    usage: toResponsesUsage(usage) || { input_tokens: 0, output_tokens: 0, total_tokens: 0 },
+    usage: {
+      input_tokens: usage.prompt_tokens || usage.input_tokens || 0,
+      output_tokens: usage.completion_tokens || usage.output_tokens || 0,
+      total_tokens: usage.total_tokens || (usage.prompt_tokens || 0) + (usage.completion_tokens || 0),
+    },
   };
 }