First real content for the `clide` Dart package at the repo root.
One AOT-compiled binary (ADR 0005) with two modes:
* `clide --daemon` long-running unix-socket server; listens on
`$XDG_RUNTIME_DIR/clide-$USER.sock` with stale-socket
reclaim, accepts JSON-lines request/response traffic, clean
SIGTERM shutdown unlinks the socket file.
* `clide <subcommand>` one-shot; opens the socket, sends a
request, writes the response JSON to stdout, exits with the
dispatcher's error code per ADR 0006 (0/1/2/3/4). Unknown
subcommands forward to the daemon so extensions can register
their own without CLI changes.
Tier 0 handlers: `ping` (returns pong + version + UTC ts) and
`version`. Both are covered by `test/ipc/` + `test/daemon/`; the
subprocess test builds `bin/clide`, starts it, pings it, SIGTERMs
it, and asserts the socket file disappears.
Co-Authored-By: Claude <noreply@anthropic.com>