Exercise 2: Different-Tag Nesting — Possible Solution
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THE TEST
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    html = "<p>Hello <b>bold</b> world</p>"
    naive_extract(html, "p")
    depth_aware_extract_first(html, "p")

RESULT
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    naive_extract:              ['Hello <b>bold</b> world']
    depth_aware_extract_first:  'Hello <b>bold</b> world'

Both approaches agree, and both are correct.

WHY THE NAIVE REGEX DOESN'T TRIP UP HERE
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naive_extract's own pattern is built specifically around ONE tag
name at a time: f"<{tag}>(.*?)</{tag}>" -- for this call, that's
literally <p>(.*?)</p>. The regex engine is only ever watching for
the exact strings "<p>" and "</p>". The <b> and </b> tags in the
middle are just ordinary characters to it, as far as the pattern
matching goes -- no different from if the text had said "Hello
*bold* world" with literal asterisks. Since there's only ONE <p> and
ONE </p> anywhere in the string, the non-greedy capture correctly
grabs everything between them, bold tag and all.

WHY SAME-TAG NESTING IS GENUINELY DIFFERENT
------------------------------
The chapter's own broken example, "<div><div>Inner</div></div>",
fails because the pattern is specifically hunting for </div> -- and
the FIRST </div> the scan encounters isn't the one that closes the
outer div at all; it's the one that closes the INNER div, which
happens to be spelled with the exact same three characters. The
regex has no way to tell "the </div> that closes the div two levels
in" apart from "the </div> that closes the outermost div" -- they
are literally the same six-character string, and a regex matches
strings, not tree positions. Nesting a DIFFERENT tag inside never
creates that ambiguity, because a different tag's own closing
sequence (</b>) can never be confused with the one the pattern is
actually searching for (</p>). The failure this chapter demonstrates
is specifically about a tag closing itself prematurely because an
identically-named tag opened again first -- not about nesting in
general.