fix: avoid reusing disturbed request bodies

[nandan-bhat]

Changes

• Make toNextRequest clone Requests when possible and skip attaching bodies that are already used/locked.
• Prevent “Response body object should not be disturbed or locked” errors in proxy/middleware flows.
• Add a regression test for consumed-body inputs.

Why

• Some proxy paths (e.g., /me/*) buffer the request body before other SDK helpers run. Re-wrapping the same Request into a NextRequest after the body is consumed throws in Node runtime.
• The new logic preserves normal behavior for fresh requests while safely handling already-used bodies.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.27%. Comparing base (7a15b30) to head (cefe1c4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2515      +/-   ##
==========================================
+ Coverage   91.22%   91.27%   +0.05%     
==========================================
  Files          39       39              
  Lines        4705     4735      +30     
  Branches      987     1001      +14     
==========================================
+ Hits         4292     4322      +30     
  Misses        407      407              
  Partials        6        6              

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