Fix fragment with path structure misparsed as a query (#172)

[gaoflow]

Fixes #172.

Summary

A URL fragment that contains path structure is silently misparsed as a query, corrupting its /:

>>> import furl
>>> str(furl.furl('https://example.com/path/#/foo=123'))
'https://example.com/path/#%2Ffoo=123'   # expected '…#/foo=123'

The / is percent-encoded to %2F — exactly the round-trip corruption reported in #172.

Cause

In Fragment.load, a fragment with no ? was routed to the query parser whenever it contained an =:

if '=' in fragment:  # Query example: '#woofs=dogs'.
    self._query.load(fragment)
else:
    self._path.load(fragment)

So #/foo=123 was treated as a query, making /foo a query key whose / is then percent-encoded on serialization. The branch had no test coverage for =-without-? inputs that also contain /.

Fix

Only treat such a fragment as a query when = precedes any / (or there is no / at all). A / before the first = signals path structure:

if '=' in fragment and (
    '/' not in fragment or fragment.find('=') < fragment.find('/')
):
    self._query.load(fragment)
else:
    self._path.load(fragment)

• #woofs=dogs → query (unchanged)
• #key=val/ue → query (unchanged — the / is in the value, after =)
• #/foo=123, #a/b=c, #/a=1&b=2 → path (the / is preserved)
• The ?-split branch (path + query) is untouched.

Verification

• Added regression cases to TestFragment.test_load (the /-before-= path cases, plus a =-before-/ query case to pin the unchanged behavior). They fail before the fix (the fragment parses as a query with an empty path) and pass after.
• Full suite: 70 passed, 3 failed — the 3 failures (test_hosts/test_netloc/test_odd_urls) are pre-existing ipaddress/urllib version drift, identical with and without this change (baseline is 69 passed / 4 failed; my new assertions account for the one-test delta).
• flake8 clean.

This pull request was prepared with the assistance of AI, under my direction and review.