feat(usage): raw request detail modal + raw stream capture

* Add /api/usage/request-details/raw endpoint serving a single
  stored request detail verbatim (raw payloads), with /raw doc
  clarifying it stays gated by the dashboard auth layer.
* Add RawDetailModal opened from a new 'Raw' button in
  RequestDetailsTab. Modal loads /raw, exposes per-section copy
  buttons and a 'Copy all (JSON)' that bundles every section.
* Capture the raw provider SSE text inside the streaming
  transform (cap 64KB) and forward it through
  onStreamComplete.rawProviderText so handler stores it as the
  providerResponse. response.content stays the extracted user
  text. Tool-call-only turns remain so the marker.
* Accumulate from translated client-facing chunks instead of
  raw provider shapes so Responses, Claude delta types, and
  Gemini/Antigravity parts all contribute.
* Drop redaction from the list endpoint; raw access is now via
  the dedicated /raw endpoint. Tests cover the new behavior.

open-sse/handlers/chatCore/streamingHandler.js

@@ -208,6 +208,7 @@ export function buildOnStreamComplete({
 		};
 		const safeContent = contentObj?.content || "[Empty streaming response]";
 		const safeThinking = contentObj?.thinking || null;
+		const rawProviderText = typeof contentObj?.rawProviderText === "string" ? contentObj.rawProviderText : "";
 
 		saveRequestDetail(
 			buildRequestDetail(
@@ -220,7 +221,7 @@ export function buildOnStreamComplete({
 					tokens: usage || { prompt_tokens: 0, completion_tokens: 0 },
 					request: extractRequestConfig(body, stream),
 					providerRequest: finalBody || translatedBody || null,
-					providerResponse: safeContent,
+					providerResponse: rawProviderText || safeContent,
 					response: {
 						content: safeContent,
 						thinking: safeThinking,