Adopt repo standards: scaffold, policies, lint-clean (closes #1)

Add the standard scaffold and bring the tree to a clean lint under the
vendored `default: all` config: `script/` Scripts-to-Rule-Them-All
entrypoints with the `Makefile` as thin shims; a `Dockerfile` whose
`lint` and `test` phases gate the build; `.gitea/workflows/` CI running
`script/cibuild`; `REPO_POLICIES.md`, `.editorconfig`, `.dockerignore`,
`LICENSE` (WTFPL), `TODO.md`, `.gitignore`. The `.golangci.yml` is
byte-identical to the canonical copy in the `prompts` repo
(`https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`).

The 211 lint findings were fixed, not suppressed: package globals became
functions/fields/a command constructor, magic numbers became named
constants, `ctx` threads into the probes, loop functions were split to
cut complexity. Behavior is unchanged; the log file mode stays `0644`.
Four `//nolint:gosec` remain — G204 on the fixed-argv subprocess calls,
G304 on the operator-chosen log file — matching the reference repos.

`make check` is green (lint and tests run in Docker).

Model: opus-4-8

internal/cli/export_test.go

@@ -0,0 +1,8 @@
+//go:build linux
+
+package cli
+
+import "github.com/spf13/cobra"
+
+// NewRootCmd exposes newRootCmd for external tests.
+func NewRootCmd() *cobra.Command { return newRootCmd() }