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

Standard scaffold: script/ entrypoints with the Makefile as thin shims, a Dockerfile whose lint and test phases gate the build, a Gitea CI workflow running script/cibuild, REPO_POLICIES.md, TODO.md, .editorconfig, .dockerignore, LICENSE, wider .gitignore. .golangci.yml is byte-identical to the canonical copy in the prompts repo.

211 lint findings fixed in code: package globals became functions/fields and a cobra command constructor, magic numbers became named constants, ctx is threaded into the probes, monitor loops split. Tests moved to external _test packages with export_test.go. Behavior unchanged.

Readers will trip over: make lint/test/check now need a Docker daemon; the personal rsync copy/run targets are gone and make run runs locally.
Disclosure: four //nolint:gosec remain on the fixed-argv ping/curl calls and the operator-chosen log file, as the reference repo annotates the same class.
Disclosure: module path left as-is.

Model: opus-4-8 (implementation); fable-5-1 (merge)

script/lint

@@ -0,0 +1,16 @@
+#!/bin/sh
+# script/lint: run the linter. golangci-lint is never installed on the host;
+# it runs only in docker, as the `lint` phase of the Dockerfile. --no-cache
+# forces the phase to re-execute, so a cached layer cannot report a pass it
+# did not earn. The build is tagged so no dangling image is left behind.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+	cd "$ROOT"
+	docker build --no-cache --target lint \
+		-t "$(script/projectname)-lint" .
+}
+
+main "$@"