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>

CHANGELOG.md

@@ -29,6 +29,7 @@ heading, and (b) bumping `project.yaml` `version:` in the same commit.
   [ADR 0002](docs/ADRs/0002-sidecar-language-go.md) — Sidecar language: Go.
   [ADR 0003](docs/ADRs/0003-pql-as-supporter-tool.md) — pql as supporter tool; wrap, don't duplicate; pql is a Clide subsystem when present.
   [ADR 0004](docs/ADRs/0004-ignore-file-strategy.md) — Ignore file strategy (`ignore_files:` in `.pql/config.yaml`, layered).
+- Go sidecar/CLI skeleton under `sidecar/` (module `git.schweitz.net/jpmschweitzer/clide/sidecar`): `cmd/clide/main.go`, `internal/cli` with a stdlib-flag dispatch, `internal/diag` mirroring pql's exit-code + stderr-JSON contract, `internal/version` with ldflag-stamped build info, and placeholder packages for `daemon`, `pty`, `proc`, `git`, `ipc`, `pql` awaiting their tier. `clide --version` emits JSON build-info today.
 - Root `Makefile` drives both the Go sidecar and the Flutter app under one toolchain. Version is read from `project.yaml` via awk and stamped into the sidecar via `-ldflags -X`. Flutter targets gracefully noop before the app is scaffolded so the Makefile is usable from day one. Pinned Go tooling (govulncheck, goimports, golangci-lint) installs via `make tools`.
 - `ci/` entry scripts: `test.sh`, `lint.sh` (includes the supply-chain gate — no green lint without a green CVE scan), `security.sh`, `release.sh` (stub).
 - Project identity files for the Flutter rebuild at the repo root: `project.yaml` (single source of truth for version + module path, version 2.0.0-dev), a fresh `README.md`, MIT `LICENSE`, and `.editorconfig`. The Python clide's manifest and README are preserved under `legacy/`.