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)

.dockerignore

@@ -0,0 +1,51 @@
+# .dockerignore does NOT use .gitignore semantics. Docker matches with
+# moby/patternmatcher: filepath.Match plus `**`, so `*` does not cross
+# `/` and an unprefixed pattern is anchored at the context root. Every
+# depth-independent pattern therefore needs `**/`; only genuinely
+# root-anchored entries go unprefixed. Never transplant these into
+# .gitignore, where `**/` is wrong.
+#
+# Matching is case-sensitive, so secrets use character ranges rather
+# than an ALL-CAPS twin, which would still miss `Server.Key`.
+
+# Excluding .git means `git describe` cannot run in any build stage and
+# fails quietly there; rtnetmon embeds no version, so this is safe.
+.git
+
+# Agent scratch: one full checkout of the repo per in-flight agent.
+# Anchored because agents run at the repo root here.
+.claude
+
+# This repo's own host-built artifacts, root-anchored so `bin/` is not
+# also matched inside package directories.
+/bin
+/rtnetmon
+main.go.old
+
+# Environment files.
+**/*.[eE][nN][vV]
+**/.[eE][nN][vV].*
+**/.[eE][nN][vV][rR][cC]
+
+# Private keys and the bundles carrying them.
+**/*.[pP][eE][mM]
+**/*.[kK][eE][yY]
+**/*.[pP]12
+**/*.[pP][fF][xX]
+**/[iI][dD]_[rR][sS][aA]
+**/[iI][dD]_[dD][sS][aA]
+**/[iI][dD]_[eE][cC][dD][sS][aA]
+**/[iI][dD]_[eE][dD]25519
+
+# OS metadata.
+**/.DS_Store
+**/Thumbs.db
+
+# Editor state.
+**/*.swp
+**/*.swo
+**/*~
+**/*.bak
+**/.idea
+**/.vscode
+**/*.sublime-*