add Go sidecar and CLI skeleton

cmd/clide/main.go is the single entry; the same binary will later
switch into sidecar-daemon mode via --daemon. internal/cli holds the
dispatch (stdlib flag for now, Cobra arrives with the first real
subcommand in Tier 2). internal/diag mirrors pql's exit-code contract
so the two tools share one mental model for callers. internal/version
exposes the build-info struct that the Makefile's -ldflags -X targets
stamp; Info() is wired to --version so the binary reports both the
declared project.yaml version and the commit it was built from.

The daemon, pty, proc, git, ipc, and pql sub-packages ship as doc.go
stubs naming the subsystem they will own. They keep the layout legible
before the code lands so tier work has a home on arrival.

Module path targets Gitea (git.schweitz.net/jpmschweitzer/clide/sidecar),
matching where the repo lives. Go module resolution works if the host
serves the meta tags; a vanity import path can be added later if
needed.

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

sidecar/internal/cli/cli.go

@@ -0,0 +1,53 @@
+// Package cli is the CLI front-end. cmd/clide/main.go calls Run with
+// os.Args[1:]. Subcommands land here one file per command once Tier 2
+// begins (see docs/initial-plan.md).
+//
+// Stdlib-only for the pre-Tier-0 scaffold. Cobra arrives with the first
+// real subcommand surface.
+package cli
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+
+	"git.schweitz.net/jpmschweitzer/clide/sidecar/internal/diag"
+	"git.schweitz.net/jpmschweitzer/clide/sidecar/internal/version"
+)
+
+// Run dispatches CLI args. Returns the process exit code per the diag
+// contract.
+func Run(args []string) int {
+	fs := flag.NewFlagSet("clide", flag.ContinueOnError)
+	fs.SetOutput(os.Stderr)
+
+	daemon := fs.Bool("daemon", false, "run as the long-running sidecar daemon")
+	showVersion := fs.Bool("version", false, "print build info and exit")
+
+	if err := fs.Parse(args); err != nil {
+		return diag.Usage
+	}
+
+	if *showVersion {
+		b, _ := json.Marshal(version.Info())
+		fmt.Println(string(b))
+		return diag.OK
+	}
+
+	if *daemon {
+		diag.Error("cli.not-implemented", "daemon mode not yet implemented", "tier 0 — sidecar scaffold lands next")
+		return diag.Software
+	}
+
+	// No subcommand yet. Surface the pql-style exit 64 so callers can tell
+	// the difference between "no instructions" and a successful run.
+	rest := fs.Args()
+	if len(rest) == 0 {
+		diag.Error("cli.usage", "no subcommand given", "see docs/initial-plan.md — Tier 2 defines the CLI surface")
+		return diag.Usage
+	}
+
+	diag.Error("cli.not-implemented", fmt.Sprintf("subcommand %q not yet implemented", rest[0]), "tier 2 lands the CLI surface")
+	return diag.Software
+}