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/x448/float16/.travis.yml

@@ -0,0 +1,13 @@
+language: go
+
+go:
+  - 1.11.x
+
+env:
+  - GO111MODULE=on 
+  
+script:
+  - go test -short -coverprofile=coverage.txt -covermode=count ./...
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)