Add the MIT license (closes #14)

sneak chose MIT for keyfunc. LICENSE holds the standard MIT text with
the line "Copyright (c) 2026 sneak". The README's first paragraph and
its License section now name MIT, and the line for this issue leaves
the README TODO list.

Model: opus-5-5

README.md

@@ -1,11 +1,10 @@
 # keyfunc
 
-`keyfunc` is a Go command-line tool by [@sneak](https://sneak.berlin) — its
-license is not yet chosen
-([#14](https://git.eeqj.de/sneak/keyfunc/issues/14)) — that turns a BIP-39
-mnemonic into SSH keys, age identities and child mnemonics, each of which can be
-recreated from that mnemonic at any time. The same mnemonic, key type and index
-always give the same key.
+`keyfunc` is an MIT-licensed Go command-line tool by
+[@sneak](https://sneak.berlin) that turns a BIP-39 mnemonic into SSH keys, age
+identities and child mnemonics, each of which can be recreated from that
+mnemonic at any time. The same mnemonic, key type and index always give the same
+key.
 
 It uses the BIP-85 entropy deriver from `git.eeqj.de/sneak/secret/pkg/bip85` and
 takes the same steps as that repository's `agehd` package.
@@ -306,14 +305,11 @@ standard: most Makefile targets are thin shims over an executable in
 
 The open issues that stand between the tree and a 1.0 release:
 
-- [#14 Choose a license and add LICENSE](https://git.eeqj.de/sneak/keyfunc/issues/14)
 - [#15 Decide the Go module path before 1.0](https://git.eeqj.de/sneak/keyfunc/issues/15)
 
 ## License
 
-Not yet chosen. The license is the owner's decision, still open on the tracker
-([#14](https://git.eeqj.de/sneak/keyfunc/issues/14)); the `LICENSE` file is added
-when that issue is answered.
+MIT. The full text is in [`LICENSE`](LICENSE).
 
 ## Author