fix(e2e): fix hermetic cassette mismatches for ai-sdk, groq, and cohere

- ai-sdk: remove "**" wildcard from ignoreBodyFields so stream vs
  non-stream requests match the correct cassette entries; the wildcard
  was causing non-streaming calls to receive SSE responses
- groq: split synthetic reasoning SSE entry into separate content and
  stop/usage chunks so x_groq.usage is captured; fix entry 3 callIndex
  from 2 to 3
- cohere: rewrite v7-14-0 cassette from /v1/{chat,embed,rerank} to
  /v2/{chat,embed,rerank} to match what client.v2.* actually calls

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Qard

e2e/helpers/cassette-filters.mjs

@@ -7,15 +7,6 @@
 
 const AI_SDK_VOLATILE_FIELDS = {
   ignoreBodyFields: [
-    // Strip ALL body fields so matching falls back to URL + method + callIndex.
-    // The AI SDK scenarios make requests in a deterministic order; the cassette
-    // entries are distinguished by position (callIndex), not by body content.
-    // This avoids spurious misses caused by the SDK adding new default fields
-    // between minor versions (e.g. Responses API drift: store, truncation, etc.)
-    // or by schema format changes in tool definitions.
-    "**",
-    // (The specific field list below is kept for documentation purposes but
-    // is superseded by the ** wildcard above.)
     // AI SDK volatile fields (change per-run)
     "experimental_generateMessageId",
     "messageId",