refactor: move version to Go source, extract in flake.nix

Define version once in cmd/oubliette/main.go and use builtins.match
in flake.nix to extract it. Add versioning guidelines to CLAUDE.md.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -14,6 +14,16 @@ SSH honeypot written in Go. See `PLAN.md` for full project plan and architecture
 - Keep code simple and focused. Refer to `PLAN.md` for design decisions.
 - When adding new config options, always add them to `oubliette.toml.example` as well.
 
+## Versioning
+
+We use **semver** (`MAJOR.MINOR.PATCH`). The version is defined in `cmd/oubliette/main.go` (`const Version`) and extracted automatically by `flake.nix`.
+
+- **Patch** (`0.1.0` → `0.1.1`): Bug fixes, minor tweaks, documentation changes.
+- **Minor** (`0.1.0` → `0.2.0`): New features, new config options, new shell types.
+- **Major** (`0.x.y` → `1.0.0`): Breaking changes to config format or public interfaces.
+
+Bump the version when merging a feature branch to master, not on every commit. While pre-1.0, breaking changes only require a minor bump.
+
 ## Git workflow
 
 - Use **conventional commits** (e.g. `feat:`, `fix:`, `refactor:`, `docs:`, `test:`, `chore:`).

cmd/oubliette/main.go

@@ -12,6 +12,8 @@ import (
 	"git.t-juice.club/torjus/oubliette/internal/server"
 )
 
+const Version = "0.1.0"
+
 func main() {
 	configPath := flag.String("config", "oubliette.toml", "path to config file")
 	flag.Parse()

flake.nix

@@ -14,11 +14,13 @@
       packages = forAllSystems (system:
         let
           pkgs = nixpkgs.legacyPackages.${system};
+          mainGo = builtins.readFile ./cmd/oubliette/main.go;
+          version = builtins.head (builtins.match ''.*const Version = "([^"]+)".*'' mainGo);
         in
         {
           default = pkgs.buildGoModule {
             pname = "oubliette";
-            version = "0.1.0";
+            inherit version;
             src = ./.;
             vendorHash = "sha256-z/E1ZDfedOxI8CSUfcpFGYX0SrdcnAYuu2p0ATozDaA=";
             subPackages = [ "cmd/oubliette" ];