fix(enable): add separate default-No push guard and warn prefix

Split the outward-facing steps of the non-repo bootstrap into independent, default-No confirmations so opting into one no longer implies the next:

• The init prompt now leads with "Warning:" so a wrong-directory run reads as the warning it is.
• Creating the GitHub repo and pushing to it are now separate guards. Even after opting into creating the repo, publishing the directory's contents requires its own confirmation (default No). Declining leaves the repo created with origin configured but nothing pushed, and prints the manual git push -u origin HEAD next step.

ghRepoCreate's final parameter now means "push" rather than "hasCommits"; the finalize step passes committed && state.push.

Tests: default-No guards for all three prompts and a finalize test that the push is skipped (repo still created) when the push decision is No. Folded the TTY/accessible env setup into a shared withInteractivePromptStdin helper and migrated the existing resolveRepoName prompt test onto it.