main side of 414: cheaper test hashing, and failing tests visible in the build log (closes #414) (#416)

The `main` side of #414: the two changes that make `next` green, and nothing else from `next`. Each is its own commit, so it can be compared with its `next` counterpart.

- #404, as merged to `next`: a test binary hashes passwords at a 1 MB Argon2id cost instead of 64 MB, `TestHashPassword_ShippedParameters` keeps the shipped cost covered, and `script/test` runs at most four packages and eight parallel tests at once. Every test that starts a database hashed the admin password at 64 MB, which on a busy host made `internal/handlers` overrun its application start and its 90-second timeout. That is what turned `main` red.
- #415: `script/test` runs without `-v`, so the build log, which the Docker build cuts off at 2 MiB, carries one result line per package and, for a package that fails, everything its tests wrote, application log lines included, instead of only passing packages.

What the diff does not show: `script/test` differs from `next` by one line. `main` has no `script/assets` yet, so it is not called. Several packages failing at once can still reach the 2 MiB limit.

- Judgement call: both commits keep their subjects from `next`, including their `closes` references.
- Deviation and not fixed here: the same two as on #415 (no `-v` rerun on failure, #315; remaining sensitivity to extreme CPU load, #225).

Model: opus-5-5
Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #416
Co-authored-by: clawbot <35+clawbot@noreply.example.org>

internal/database/export_test.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"log/slog"
 	"os"
+	"testing"
 	"time"
 
 	"go.uber.org/fx"
@@ -79,3 +80,14 @@ func (d *Database) ExportSetBannerOut(w io.Writer) {
 func DummyPasswordHashForTest() string {
 	return dummyPasswordHash()
 }
+
+// HashAtShippedCostForTest makes HashPassword hash at the shipped
+// memory cost until t ends. t must not run in parallel with other
+// tests, which would hash at that cost alongside it.
+func HashAtShippedCostForTest(t *testing.T) {
+	t.Helper()
+
+	hashAtShippedCostInTest = true
+
+	t.Cleanup(func() { hashAtShippedCostInTest = false })
+}