homelab: add tf verbs + stack/git-crypt substrate

Adds the tf verb-group and the resolver substrate beneath it, continuing the
v0.1 infra-loop build.

- substrate: findInfraRoot (walk up to terragrunt.hcl + stacks/), stack→dir
  resolver, and repo/remote/git-crypt detection (preferRemote forgejo>origin,
  hasGitCryptAttr, gitCryptFlags) — the last is for `work` next.
- tf plan/validate/fmt/force-unlock/apply, resolving the stack from cwd and
  delegating to scripts/tg (which owns state decrypt/encrypt, the Vault lock,
  and the ingress auth-comment check) rather than calling terragrunt directly.
- tf apply is presence-coupled: claims stack:<name>, ALWAYS releases on exit
  (normal, error, or SIGINT/SIGTERM via sync.Once + signal handler) — fixing
  the documented ~200-claim leak — and prints an out-of-band reminder since CI
  applies canonically on push.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cli/repo_test.go

@@ -0,0 +1,37 @@
+package main
+
+import "testing"
+
+func TestPreferRemote(t *testing.T) {
+	cases := []struct {
+		in   []string
+		want string
+	}{
+		{[]string{"origin", "forgejo"}, "forgejo"},
+		{[]string{"forgejo"}, "forgejo"},
+		{[]string{"origin"}, "origin"},
+		{[]string{"upstream"}, "upstream"},
+		{nil, ""},
+	}
+	for _, c := range cases {
+		if got := preferRemote(c.in); got != c.want {
+			t.Errorf("preferRemote(%v) = %q, want %q", c.in, got, c.want)
+		}
+	}
+}
+
+func TestHasGitCryptAttr(t *testing.T) {
+	if !hasGitCryptAttr("*.tfvars filter=git-crypt diff=git-crypt") {
+		t.Error("expected git-crypt detected")
+	}
+	if hasGitCryptAttr("*.md text\n*.png binary") {
+		t.Error("expected no git-crypt")
+	}
+}
+
+func TestGitCryptFlagsShape(t *testing.T) {
+	f := gitCryptFlags()
+	if len(f) != 6 || f[0] != "-c" || f[1] != "filter.git-crypt.smudge=cat" {
+		t.Fatalf("unexpected git-crypt flags: %v", f)
+	}
+}