Add Nix flake for mciasctl and mciasgrpcctl

Vendor dependencies and expose control program binaries via
nix build. Uses nixpkgs-unstable for Go 1.26 support.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/golang-migrate/migrate/v4/source/parse.go

@@ -0,0 +1,40 @@
+package source
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+)
+
+var (
+	ErrParse = fmt.Errorf("no match")
+)
+
+var (
+	DefaultParse = Parse
+	DefaultRegex = Regex
+)
+
+// Regex matches the following pattern:
+//
+//	123_name.up.ext
+//	123_name.down.ext
+var Regex = regexp.MustCompile(`^([0-9]+)_(.*)\.(` + string(Down) + `|` + string(Up) + `)\.(.*)$`)
+
+// Parse returns Migration for matching Regex pattern.
+func Parse(raw string) (*Migration, error) {
+	m := Regex.FindStringSubmatch(raw)
+	if len(m) == 5 {
+		versionUint64, err := strconv.ParseUint(m[1], 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		return &Migration{
+			Version:    uint(versionUint64),
+			Identifier: m[2],
+			Direction:  Direction(m[3]),
+			Raw:        raw,
+		}, nil
+	}
+	return nil, ErrParse
+}