fix(cli): add 'setup' as an alias for the install command (fixes #4112)

Discord support and other guidance still tell users 'bunx oh-my-opencode setup', but the CLI only registers 'install'. Running the recommended command produces:

  error: unknown command 'setup'

which dead-ends users who are trying to refresh missing skills (hyperplan, etc.) after upgrading. Commander.js supports first-class aliases, so declaring '.alias("setup")' on the install command makes both names route to the same action without any code duplication. Help output now reads 'Usage: oh-my-opencode install|setup [options]', which is the right discovery hint for both newcomers and users following older docs.

Regression test parses cli-program.ts and asserts the install command block contains '.alias("setup")' before its '.action(' so a future refactor of the CLI cannot silently drop the alias.

src/cli/cli-program.ts

@@ -24,6 +24,7 @@ program
 
 program
   .command("install")
+  .alias("setup")
   .description("Install and configure oh-my-opencode with interactive setup")
   .option("--no-tui", "Run in non-interactive mode (requires all options)")
   .option("--claude <value>", "Claude subscription: no, yes, max20")