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/version/version.go

@@ -0,0 +1,35 @@
+// Package version exposes build-info stamped via -ldflags at build time.
+// See the root Makefile's LDFLAGS for the -X targets.
+package version
+
+import "runtime"
+
+var (
+	Version = "dev"
+	Commit  = "unknown"
+	Date    = "unknown"
+)
+
+// SchemaVersion tracks the app↔sidecar IPC contract. Bump when the wire
+// format changes in a way that requires coordinated app and sidecar
+// updates. Mirror in project.yaml `schema_version:` when that field is
+// added there.
+const SchemaVersion = 0
+
+type BuildInfo struct {
+	Version       string `json:"version"`
+	Commit        string `json:"commit"`
+	Date          string `json:"date"`
+	GoVersion     string `json:"go_version"`
+	SchemaVersion int    `json:"schema_version"`
+}
+
+func Info() BuildInfo {
+	return BuildInfo{
+		Version:       Version,
+		Commit:        Commit,
+		Date:          Date,
+		GoVersion:     runtime.Version(),
+		SchemaVersion: SchemaVersion,
+	}
+}