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/run.go

@@ -9,7 +9,13 @@ import (
 // the caller sees live output, and returns the command's error (non-nil on
 // non-zero exit — preserved so homelab's own exit code reflects the child's).
 func runStreaming(name string, args ...string) error {
+	return runStreamingIn("", name, args...)
+}
+
+// runStreamingIn is runStreaming with a working directory (empty = inherit).
+func runStreamingIn(dir, name string, args ...string) error {
 	cmd := exec.Command(name, args...)
+	cmd.Dir = dir
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	cmd.Stdin = os.Stdin