Closes #75.

Problem

tracebloc data ingst (and the same for cluster, auth, client) printed the group's help and exited 0 — a mistyped subcommand looked like success. Verified on develop: data ingst, cluster inf, client lst all exit 0.

Root cause (corrects the issue's proposed fix): a parent command with subcommands but no Run/RunE is not runnable, and cobra short-circuits a non-runnable command to flag.ErrHelp before it validates args (command.go: if !c.Runnable() { return flag.ErrHelp } precedes ValidateArgs). So the unknown token never reached validation. cobra.NoArgs does not fix this — it's an arg validator, never reached on a non-runnable command.

Fix

Give the four group commands a RunE: runGroup (in root.go):

• bare tracebloc <group> → prints help, exits 0 (unchanged);
• mistyped subcommand → hard error, exit 1, with a nearest-match suggestion, mirroring the unknown command wording the root already emits via cobra's default legacyArgs.

SuggestionsMinimumDistance: 2 drives the hint; SuggestionsFor skips hidden commands, so the Rev-9 hidden client list is never suggested. The root command is untouched (it already errored correctly).

$ tracebloc data ingst
Error: unknown command "ingst" for "tracebloc data"

Did you mean this?
	ingest

Run 'tracebloc data --help' for the available commands.   # exit 1

Tests (internal/cli/group_test.go)

• UnknownSubcommand_Errors — all four groups + the dataset alias, asserts non-zero exit + "unknown command".
• UnknownSubcommand_Suggests — nearest-match hint (ingst→ingest, inf→info, doctr→doctor).
• HiddenSubcommand_NotSuggested — client lst must not surface the hidden list.
• Bare_StillHelpsExitZero — bare group still helps + exits 0.

The error cases are verified to fail without the fix. Full internal/... suite + go vet + gofmt green.

Targets develop. Isolated to root.go + the four group constructors — no overlap with the open ingest-path PRs.

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