Re-vendor the canonical files from sneak/prompts at dd4027b (closes #112)

The shared files are fetched from sneak/prompts dd4027b, with this
repository's own entries after the shared content in .gitignore,
.editorconfig and .dockerignore.

Lint and tests are Dockerfile phases (golangci-lint v2.14.0, Debian Go
1.24.13) that the build stage depends on, and the Makefile targets call
the script/ entrypoints. make fmt also formats Markdown with prettier.

Fixes for the new lint findings: the auth cookie is always Secure, an
IRC connection's relay goroutine stops when the connection closes, and
repeated strings are constants.

Model: opus-5-5

pkg/irc/numerics.go

@@ -68,6 +68,7 @@ const (
 // Command responses (200-399).
 const (
 	// RFC 2812 trace/stats/links replies (200-219).
+
 	RplTraceLink       IRCMessageType = 200
 	RplTraceConnecting IRCMessageType = 201
 	RplTraceHandshake  IRCMessageType = 202
@@ -224,7 +225,7 @@ const (
 
 // names maps numeric codes to their standard IRC names.
 //
-//nolint:gochecknoglobals
+//nolint:gochecknoglobals,gosec // G101: IRC numeric names, not credentials
 var names = map[IRCMessageType]string{
 	RplWelcome:  "RPL_WELCOME",
 	RplYourHost: "RPL_YOURHOST",