Fix string with escape characters using existing string with escaped characters

[jordoh]

After packing a string containing an escaped character, a subsequent string containing the escape character would erroneously use the string with the escaped character. I've included a test that demonstrates this behavior.

This PR updates the string re-use check to escape the string before checking for a matching string in the dictionary.

[rgcl]

Hi @jordoh — first of all, I sincerely apologize for the 3-year wait on this. The project had been abandoned for years and I'm only now coming back to it.

Your diagnosis is correct: the lookup was comparing against unencoded strings while the dictionary stored encoded ones, so strings with special characters were never deduplicated. That's a real bug and your fix is clean.

I'm going to close this in favor of #27, which fixes the exact same issue but as part of a broader refactor that switches the dictionary from arrays to objects (O(1) lookup). Since both touch the same lines and #27 covers your fix, merging both would create unnecessary conflicts.

Your contribution helped confirm the bug and the test you added is genuinely useful. Thank you.