feat(cli): add help for all commands

emcli had only raw flag usage and no command listing; `--help` on agent commands
even emitted a JSON error envelope and exited 2. Add real help:

- Top-level `emcli` / `help` / `-h` / `--help` prints a grouped command catalogue
  (agent vs admin) with one-line summaries and the EMCLI_KEY/EMCLI_DB env vars.
- `emcli help <command>` prints that command's synopsis + summary.
- `emcli <command> --help` prints synopsis + summary + flags and exits 0. Agent
  commands keep stdout JSON-free (usage goes to stderr); admin commands print to
  stdout. Help works without EMCLI_KEY (no DB access).
- help.go holds the command catalogue; flag.ErrHelp is handled as success, and
  admin handlers short-circuit help before opening the store.

Unknown commands still error (exit 2). Full suite passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/cli/admin.go

@@ -12,8 +12,12 @@ import (
 
 // runAccount handles `account add|list`. Human-readable output (never JSON).
 func runAccount(args []string, out, errOut io.Writer) int {
-	if len(args) == 0 {
-		fmt.Fprintln(errOut, "usage: emcli account <add|list>")
+	if len(args) == 0 || helpRequested(args[0]) {
+		printCmdUsage(out, "account")
+		fmt.Fprintln(out, "\nSubcommands: add, edit, remove, list")
+		if len(args) > 0 {
+			return 0 // explicit --help
+		}
 		return 2
 	}
 	sub, rest := args[0], args[1:]
@@ -188,6 +192,13 @@ func auditList(st *store.Store, account string, limit int, out io.Writer) error
 
 // runConfig handles `config set <key> <value>` and `config get <key>`.
 func runConfig(args []string, out, errOut io.Writer) int {
+	if len(args) == 0 || helpRequested(args[0]) {
+		printCmdUsage(out, "config")
+		if len(args) > 0 {
+			return 0
+		}
+		return 2
+	}
 	if len(args) < 2 {
 		fmt.Fprintln(errOut, "usage: emcli config <set|get> <key> [value]")
 		return 2
@@ -236,6 +247,10 @@ func runConfig(args []string, out, errOut io.Writer) int {
 
 // runAudit handles `audit list [--account <name>] [--limit N]`.
 func runAudit(args []string, out, errOut io.Writer) int {
+	if len(args) > 0 && helpRequested(args[0]) {
+		printCmdUsage(out, "audit")
+		return 0
+	}
 	if len(args) == 0 || args[0] != "list" {
 		fmt.Fprintln(errOut, "usage: emcli audit list [--account <name>] [--limit N]")
 		return 2
@@ -262,6 +277,13 @@ func runAudit(args []string, out, errOut io.Writer) int {
 
 // runWhitelist handles `whitelist <in|out> add --account NAME --address A`.
 func runWhitelist(args []string, out, errOut io.Writer) int {
+	if len(args) == 0 || helpRequested(args[0]) {
+		printCmdUsage(out, "whitelist")
+		if len(args) > 0 {
+			return 0
+		}
+		return 2
+	}
 	if len(args) < 2 {
 		fmt.Fprintln(errOut, "usage: emcli whitelist <in|out> <add|remove|list> [flags]")
 		return 2