feat(cli): scaffold nc CLI with list-groups command

Adds a transport-agnostic CLI control plane shared between three eventual
callers (host shell, Claude in project, container agent) — though only the
host-side socket transport is wired in this commit. Container DB transport
and approval flow land alongside the first risky command.

- src/cli/frame.ts:        wire format (RequestFrame, ResponseFrame, CallerContext)
- src/cli/registry.ts:     command registry with RiskClass
- src/cli/dispatch.ts:     transport-agnostic dispatcher
- src/cli/transport.ts:    Transport interface
- src/cli/socket-client.ts: SocketTransport against data/nc.sock
- src/cli/socket-server.ts: host-side listener (chmod 0600, line-delimited JSON)
- src/cli/format.ts:       human table / --json output modes
- src/cli/client.ts:       `nc` argv -> frame -> transport -> stdout
- src/cli/commands/list-groups.ts: first command (riskClass: safe)
- bin/nc:                  bash launcher (resolves project root via symlink)
- src/index.ts:            start/stop server + import command barrel

`data/nc.sock` is intentionally separate from `data/cli.sock` (which the
existing chat-style channel adapter still owns).

Verified end-to-end: `nc list-groups`, `nc list groups`, `--json`,
unknown-command error, host-down ENOENT message with start instructions.
typecheck clean; eslint reports only the same `no-catch-all` warnings the
rest of the codebase has.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bin/nc

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+#
+# nc — NanoClaw CLI launcher.
+#
+# Resolves the project root from this script's location, cd's there so the
+# host-resolved DATA_DIR matches the running host, and execs the TS entry
+# via tsx. Symlink this file into a directory on your PATH (or alias `nc`
+# to its full path) to invoke from anywhere:
+#
+#   ln -s "$(pwd)/bin/nc" /usr/local/bin/nc
+#   # or
+#   alias nc="$(pwd)/bin/nc"
+
+set -euo pipefail
+
+SCRIPT="${BASH_SOURCE[0]}"
+# Resolve symlinks so PROJECT_ROOT points at the real checkout.
+while [ -h "$SCRIPT" ]; do
+  DIR="$(cd -P "$(dirname "$SCRIPT")" && pwd)"
+  SCRIPT="$(readlink "$SCRIPT")"
+  [[ "$SCRIPT" != /* ]] && SCRIPT="$DIR/$SCRIPT"
+done
+SCRIPT_DIR="$(cd -P "$(dirname "$SCRIPT")" && pwd)"
+PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_ROOT"
+exec pnpm exec tsx src/cli/client.ts "$@"