bug(test): main panics under -tags=e2e in loadDotEnv(nil)

[chrisnestrud]

Summary

The tagged e2e suite cannot start on main. TestMain calls loadDotEnv(nil),
and loadDotEnv calls t.Log on the nil testing.TB when it walks past the
repo root without finding .env.test, so the process panics before any test
runs.

Repro

go test -tags=e2e ./internal/e2e/

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x80 pc=...]

goroutine 1 [running]:
moonbridge/internal/e2e_test.loadDotEnv({0x0, 0x0})
	internal/e2e/e2e_test.go:235
moonbridge/internal/e2e_test.TestMain(...)
	internal/e2e/e2e_test.go:145

Root cause

e2e_test.go:145 passes nil to loadDotEnv, and e2e_test.go:235 calls
t.Log(".env.test not found — relying on OS env vars") unconditionally. Any run
that reaches the repo-root branch panics on the nil TB.

Fix

Guard the log call:

if t != nil {
	t.Log(".env.test not found — relying on OS env vars")
}

Related

• test(e2e): restore Google tool-use and multi-plugin hook coverage #101 tracks the tagged suite being unusable for other reasons (Google
  tool-use and multi-plugin hook coverage).
• fix: preserve Responses reasoning stream lifecycle #103 currently carries this guard so its reasoning-lifecycle e2e test can
  run; extracting it here lets fix: preserve Responses reasoning stream lifecycle #103 drop an unrelated file change.