Seed from go-template-repo, renamed to simplexcalc

The template's files at a77fd30, without its history or LICENSE, after
script/rename simplexcalc.

Model: opus-5-5

internal/config/export_test.go

@@ -0,0 +1,17 @@
+package config
+
+// Load is load, exported for the external test package.
+//
+// The tests live in config_test rather than config so that they drive
+// this package the way the rest of the program does — through its
+// exported surface — and cannot quietly depend on an internal detail.
+// The one thing they need that is not exported is the ability to
+// supply an environment instead of reading the process's, which is a
+// testing seam and not API.
+//
+//nolint:gochecknoglobals // a test seam, not mutable state.
+var Load = load
+
+// CSRFKeyBytes is the required key length, so the tests can assert on
+// it without restating the number.
+const CSRFKeyBytes = csrfKeyBytes