I4 [CRIT/CLI] Cross-NS verb redirects + subcommand typo suggestions (audit-I5 + audit-I6)

[espadonne]

Summary

Two CLI papercuts that turn a typo into a wild-goose chase:

• audit-I5: cobra's "Did you mean?" suggestion only fires at the root command's auto-error path. Once execution reaches a parent's RunE (which I3 landed across every parent), the suggestion machinery is bypassed. shithub reepo suggests repo, but shithub pr klose / org liat / repo cre got no help. Now they do — extended ParentRunE to walk the parent's children and Levenshtein-match (or 3+ char prefix-match) against the bad arg. shithub pr klose → Did you mean this? close.

• audit-I6: the H2 cross-namespace verb redirects help when symmetric verbs (view, close, reopen, edit) hit the wrong side — shithub pr close 1 on an issue says try 'shithub issue close 1'. But the same template fires for asymmetric PR-only verbs (pr ready, pr merge, pr review), suggesting shithub issue ready 1 — a command that doesn't exist. The user chases a dead command. Added an Asymmetric flag to ErrWrongNamespace + a CheckAsymmetric helper; the three PR-only callers now emit:

pr ready: #1 is an issue; `pr ready` only applies to pull requests (run `shithub issue view 1` to inspect)

instead of the misleading try shithub issue ready 1 redirect.

Test plan

• TestParentRunE_LevenshteinSuggestion — klose → close
• TestParentRunE_PrefixSuggestion — cre → create
• TestParentRunE_NoCloseMatchSkipsSuggestion — far-off typos don't trigger
• TestParentRunE_HiddenChildrenIgnored — hidden subs stay hidden
• TestCheckAsymmetric_PRReadyOnIssue — asymmetric flag suppresses issue ready suggestion
• TestCheckAsymmetric_PRMergeOnIssue — same for pr merge
• TestCheck_StillSuggestsForSymmetricVerb — regression guard: symmetric verbs (pr close) still redirect at issue close
• Existing TestReadyWrongNamespaceRedirects updated for the new asymmetric message
• make ci clean
• golangci-lint run clean
• Smoke dogfood: shithub pr klose / org liat / repo cre all suggest the right verb

Design notes

• Check stays as a thin wrapper around CheckAsymmetric(..., false) so the 7 existing call sites for symmetric verbs (issue close, issue edit, issue reopen, pr close, etc.) don't need to change. Only the 3 asymmetric callers (pr ready, pr merge, pr review) opt into the new path.
• Levenshtein implementation is inline (~30 lines) — no new dep, sized for the ~10-15 children per parent. Distance threshold = 2 (cobra's default), prefix-match wins outright for prefixes of length 3+.
• I deliberately did NOT extend CheckAsymmetric to also drop the symmetric verbs from the issue side onto the PR side (e.g. issue lock → pr lock). H2 already handles those, and issue→PR asymmetry isn't in the I-audit.