fix: preserve raw headers in dispatch handler bridge

[mcollina]

Description

Preserve rawHeaders and rawTrailers on the synthetic controller used by UnwrapHandler when bridging modern dispatch handlers to the legacy handler interface.

This keeps Node.js bundled fetch compatible with an imported Undici v7 Agent, so response headers remain visible and compressed bodies continue to be decoded.

Fixes: #5341

Changes

• store rawHeaders on the controller before invoking onRequestUpgrade / onResponseStart
• store rawTrailers before invoking onResponseEnd
• expose the optional controller fields in types/dispatcher.d.ts
• add a regression test covering Node.js global fetch with both the global dispatcher and an explicit dispatcher: new Agent()

Testing

• npm run lint -- lib/handler/unwrap-handler.js test/node-test/global-dispatcher-version.js types/dispatcher.d.ts
• npx borp -p "test/node-test/global-dispatcher-version.js"
• source ~/.nvm/nvm.sh && nvm use 26.3.0 >/dev/null && npx borp -p "test/node-test/global-dispatcher-version.js"

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.90%. Comparing base (d7aeee3) to head (7ecea4c).

Additional details and impacted files

@@            Coverage Diff             @@
##             v7.x    #5345      +/-   ##
==========================================
- Coverage   92.91%   92.90%   -0.01%     
==========================================
  Files         112      112              
  Lines       35837    35843       +6     
==========================================
+ Hits        33297    33299       +2     
- Misses       2540     2544       +4     

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