test(abort-reason): de-flake using synthetic transport rejection (follow-up to #120)

[productdevbook]

Applies same fix as #122 to test/abort-reason.test.ts. Reviewer of #122 flagged this as the same flake class. 5/5 clean runs after fix.

[github-actions]

Bench results

⚠️ 1 misina row(s) >5% slower than base.

benchmark	base avg	head avg	Δ
retry on 503 → 200 :: misina — retry 1× then 200	1.75 ms	1.92 ms	🔴 +9.5%
steady-state GET (200 OK, JSON parse) :: native fetch	335.46 µs	342.69 µs	· +2.2%
createMisina cold start :: createMisina({ use: [bearer] })	581.2 ns	581.4 ns	· +0.0%
POST JSON body :: ofetch	359.56 µs	358.13 µs	· -0.4%
POST JSON body :: misina	522.49 µs	516.59 µs	· -1.1%
steady-state GET (200 OK, JSON parse) :: misina	327.43 µs	323.69 µs	· -1.1%
plugin overhead (no plugins / 1 hook plugin / 3 plugins inc. wrapping) :: misina — no plugins	283.39 µs	279.78 µs	· -1.3%
hooks overhead (no hooks vs 5 hooks) :: misina — no hooks	292.67 µs	288.23 µs	· -1.5%
POST JSON body :: axios	332.32 µs	327.23 µs	· -1.5%
hooks overhead (no hooks vs 5 hooks) :: misina — 5 hooks	291.66 µs	286.99 µs	· -1.6%
steady-state GET (200 OK, JSON parse) :: ky	322.31 µs	316.49 µs	· -1.8%
createMisina cold start :: createMisina({ use: [bearer, tracing, breaker] })	1.96 µs	1.91 µs	· -2.6%
plugin overhead (no plugins / 1 hook plugin / 3 plugins inc. wrapping) :: misina — bearer + tracing + breaker	318.11 µs	308.49 µs	· -3.0%
POST JSON body :: native fetch	389.55 µs	374.96 µs	· -3.7%
plugin overhead (no plugins / 1 hook plugin / 3 plugins inc. wrapping) :: misina — bearer	297.14 µs	285.68 µs	· -3.9%
POST JSON body :: ky	492.31 µs	468.58 µs	· -4.8%
steady-state GET (200 OK, JSON parse) :: axios	346.90 µs	324.38 µs	🟢 -6.5%
steady-state GET (200 OK, JSON parse) :: ofetch	310.55 µs	276.99 µs	🟢 -10.8%
createMisina cold start :: createMisina()	1.29 µs	1.07 µs	🟢 -17.0%

_{Local Node HTTP server, Apple-class GitHub runner. Numbers fluctuate ±2-3% from runner heat alone — only sustained >5% deltas are signal.}