Romaji to Kana Converter: Astro — Chapter 2, Exercise 1
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TASK
Build the complete KANA_MAP (vowels through yōon) and the final,
correct convert() function in src/lib/convert.ts, then run it against
"sushi", "kyaku", and "gakusei" (学生, student), confirming correct
hiragana and katakana output for all three against real node output.

SOLUTION

With the complete KANA_MAP and the longest-to-shortest convert()
function from the chapter in place, running:

  console.log(convert('sushi'));
  console.log(convert('kyaku'));
  console.log(convert('gakusei'));

against real node produces:

  { hiragana: 'すし', katakana: 'スシ' }
  { hiragana: 'きゃく', katakana: 'キャク' }
  { hiragana: 'がくせい', katakana: 'ガクセイ' }

Tracing "gakusei" through the tokenizer by hand confirms why this
result is correct: at position 0, length 3 ("gak") fails, but length
2 ("ga") is a valid token (が), so it matches there and advances to
position 2. From position 2, "kus" fails but "ku" matches (く),
advancing to position 4. From position 4, "sei" fails but "se"
matches (せ), advancing to position 6, leaving only "i" left, which
matches the vowel token directly (い). The four tokens が-く-せ-い
concatenate into がくせい -- four real kana for a four-syllable word,
exactly matching the verified node output.

WHY THIS WORKS AS AN ANSWER
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It doesn't just assert the three outputs are correct -- it re-derives
one of them ("gakusei") token by token against the same
longest-to-shortest matching rule the chapter itself established,
confirming the real node output isn't a coincidence but the expected
result of the algorithm working as designed.