comprehensive completion generation: native, manpage, --help

Three-strategy pipeline with priority: native completion generators
(e.g. CMD completions nushell) > manpage parsing > --help fallback.
Single `generate` command produces one module-wrapped .nu file per
command. Parallel execution scaled to cores, 200ms timeouts, ELF
string scanning to skip binaries without -h support, native gzip
decompression via camlzip, SYNOPSIS-based subcommand detection,
nix3 manpage strategy, deduplication, nushell builtin exclusion.

lib/parser.ml

@@ -128,12 +128,15 @@ let param_parser =
          space_upper_param; space_type_param ]
      >>| fun a -> Some a)
 
-(* Switch parser: -a, --all | -a | --all *)
+(* Switch parser: -a, --all | --all / -a | -a | --all *)
 let switch_parser =
   choice
     [
       (short_switch >>= fun s ->
        comma *> long_switch >>| fun l -> Both (s, l));
+      (long_switch >>= fun l ->
+       inline_ws *> char '/' *> inline_ws *>
+       short_switch >>| fun s -> Both (s, l));
       (short_switch >>| fun s -> Short s);
       (long_switch >>| fun l -> Long l);
     ]
@@ -219,10 +222,15 @@ let entry =
 (* --- Subcommand parsing --- *)
 
 (* A subcommand line: "  name   description" *)
+let is_subcommand_char = function
+  | 'a' .. 'z' | 'A' .. 'Z' | '0' .. '9' | '-' | '_' -> true
+  | _ -> false
+
 let subcommand_entry =
   inline_ws *>
-  take_while1 (fun c -> c <> ' ' && c <> '\t' && c <> '\n') >>= fun name ->
-  (* Must have at least 2 spaces before description *)
+  take_while1 is_subcommand_char >>= fun name ->
+  if String.length name < 2 then fail "subcommand name too short"
+  else
   char ' ' *> char ' ' *> inline_ws *>
   rest_of_line <* eol >>| fun desc ->
   { name; desc = String.trim desc }