cod should check for existing completions for aliased commands

[zachriggle]

I have a bunch of wrapper scripts around ripgrep rg, and I alias all of their completions to rg since the arguments get passed-through.

Autocompletion already works in this manner, so cod should not try to learn them.

$ cat bin/example-script
#!/usr/bin/env zsh
rg "$@"

$ example-script <tab>
 -- option --
--after-context                 -A  -- specify lines to show after each match
--and                               -- Logical AND
--auto-hybrid-regex                 -- dynamically use PCRE2 if necessary
--before-context                -B  -- specify lines to show before each match
--binary                            -- search binary files, don't print binary data
--block-buffered                    -- force block buffering
--byte-offset                   -b  -- show 0-based byte offset for each matching line
--case-sensitive                -s  -- search case-sensitively

However, cod tries to learn it when passing --help.

$ example-script --help
...
OPTIONS:
    -A, --after-context <NUM>
...
┌──> /Users/zachriggle/..../bin/example-script --help
└─── cod: learn this command? [yn?] >

Here's how they are registered, tldr is compdef mycommand=rg.

#!/usr/bin/env zsh
BINDIR="${0:h}/bin"
path=("$BINDIR" $path)

for script in "$BINDIR"/*(*); do
    name="$script:t"
    compdef "$name"=rg
done

There is no fpath entry for these, they are just compdef aliases. This should be consulted before offering to learn a command.