fix(h2): detach upgrade close handler after GOAWAY

[pacocartones]

This relates to...

Fixes #5638.

Rationale

When GOAWAY marks an upgrade stream as unaccepted, severRequestStream()
already releases its HTTP/2 session. Upgrade streams also retain
onUpgradeStreamClose, which later attempts the same release after the stream
closes. The second release dereferences a cleared session and escapes as an
uncaught exception.

Detaching that upgrade-specific close handler at sever time makes the cleanup
ownership unambiguous. The request remains on the existing GOAWAY retry/error
path and settles normally.

Changes

• Detach onUpgradeStreamClose along with the regular request close handler.
• Add a raw h2c regression test: GOAWAY with lastStreamID = 0 while a CONNECT
  stream is opening must settle rather than crash the process.

Validation

• HTTP/2 core suite: 98 passed, 1 skipped.
• ESLint passed for the changed implementation and test.

Implementation and validation used Codex assistance; I reviewed the final diff and results.

Verification

Every command below was run and its output captured verbatim. The record is reproducible — the exact commands are included so you can re-run them yourself.

red — without detaching the upgrade close handler (must fail without the fix)

$ node --test --test-timeout=35000 --test-force-exit test/issue-5638.js
[…]
ℹ duration_ms 305.762
✖ failing tests:
test at test\issue-5638.js:21:1
✖ h2 CONNECT settles when GOAWAY names an older stream (29.0696ms)
  TypeError: Cannot read properties of null (reading 'Symbol(open streams)')
      at closeStreamSession (~\AppData\Local\Temp\undici-5638-repro\lib\dispatcher\client-h2.js:767:11)
      at ClientHttp2Stream.onUpgradeStreamClose (~\AppData\Local\Temp\undici-5638-repro\lib\dispatcher\client-h2.js:781:3)
      at Object.onceWrapper (node:events:622:28)
      at ClientHttp2Stream.emit (node:events:508:28)
      at emitCloseNT (node:internal/streams/destroy:148:10)
      at emitErrorCloseNT (node:internal/streams/destroy:130:3)
      at process.processTicksAndRejections (node:internal/process/task_queues:90:21)
[exit code 1]

green — fix intact (must pass) — 3 runs, identical exit code

$ node --test --test-timeout=35000 --test-force-exit test/issue-5638.js
✔ h2 CONNECT settles when GOAWAY names an older stream (35.6737ms)
ℹ tests 1
ℹ suites 0
ℹ pass 1
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 346.9513
[exit code 0]

Environment and output hashes

so: Windows 11 (AMD64)
python: 3.13.14
node --version: v24.14.1
git rev-parse HEAD: 964ce931029fdcd48fca24adbc15c42f58b82162
git status --short:
sha256(red — without detaching the upgrade close handler run 1) = 8fcf06da733ec7cd…  exit 1  0.43s
sha256(green — fix intact run 1) = 6d0099dbf983e900…  exit 0  0.47s
sha256(green — fix intact run 2) = 8848a52d1b4728cc…  exit 0  0.48s
sha256(green — fix intact run 3) = 8f41e847e930672b…  exit 0  0.43s
acta: 0fba181ecbcf4801

Status

• I have read and agreed to the Developer's Certificate of Origin.
• Tested.
• Documented by regression coverage.

[mcollina]

why is it a draft?

[pacocartones]

It’s now ready for review — thanks!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.40%. Comparing base (b111adb) to head (964ce93).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5641      +/-   ##
==========================================
- Coverage   93.40%   93.40%   -0.01%     
==========================================
  Files         110      110              
  Lines       38645    38648       +3     
==========================================
+ Hits        36098    36099       +1     
- Misses       2547     2549       +2     

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[mcollina]

lgtm