fix(loop): guard the top-level --interactive shortcut with a TTY check

[KhaiTrang1995]

Problem

cmdWizard() (loop wizard --interactive) already gates the interactive
path on process.stdin.isTTY, falling back to printNonInteractiveHelp()
otherwise. The top-level loop --interactive shortcut in main() never
had the same guard: it called runInteractiveWizard() unconditionally.

readline's question() resolves immediately with '' when stdin isn't a
TTY (a CI step, piped input, < /dev/null) instead of waiting for a
human. Without the guard, loop --interactive in a non-interactive
context silently ran the wizard with every prompt answered blank, then
executed the resulting default plan -- loop init . --pattern daily-triage --tool grok against the current directory -- scaffolding
files nobody asked for instead of printing help.

Fix

Mirrors cmdWizard()'s existing gate at the other --interactive entry
point.

Test plan

Added a regression test that runs loop --interactive with stdin
closed (execFileSync's input: '', matching < /dev/null) in an empty
temp directory, asserting it prints the non-interactive help and the
directory stays empty. Confirmed it fails with the wizard prompts
printed and no help text when the guard is stripped, and passes with
the fix. Full clean rebuild + npm test: 11/11 passing.

[cobusgreyling]

Mirrors the existing cmdWizard() TTY gate. Non-TTY loop --interactive was silently running the default init plan; help + no scaffold is the right behavior. Regression test with closed stdin is solid.