Preserve real parse diagnostics instead of the generic section wrapper

[ctoth]

Fixes #12.

The problem

Both generic section loops caught everything and replaced it with one message:

except Exception:
    self.parse_fail("Error reading section %r" % section_name)

That discarded the precise ParseError an inner reader had already raised, and it
laundered real internal bugs into what looked like a file-format complaint.

The fix

• Both section loops (AreaFile.load_sections, the Smaug/SWR loop) re-raise
  ParseError untouched, and include repr(error) when wrapping anything else, so an
  internal error is still identifiable as one.
• load_smaug_vnum_section / load_swr_vnum_section slice instead of index when
  peeking at the character after # (self.data[self.index + 1:self.index + 2]), so a
  file ending in # ends the section rather than raising IndexError.
• CircleAreaFile.read_record_header raises a located ParseError on a non-numeric
  record header instead of letting int() escape a bare ValueError.

No new abstraction; three small edits plus a test file.

Verification

test_error_reporting.py (6 tests) covers all four behaviours. With the source change
stashed, all six fail:

FAILED test_error_reporting.py::test_rom_section_error_keeps_the_specific_parse_message
FAILED test_error_reporting.py::test_smaug_section_error_keeps_the_specific_parse_message
FAILED test_error_reporting.py::test_non_parse_errors_are_reported_with_the_original_error
FAILED test_error_reporting.py::test_vnum_section_tolerates_a_trailing_hash_at_end_of_file[SmaugAreaFile]
FAILED test_error_reporting.py::test_vnum_section_tolerates_a_trailing_hash_at_end_of_file[SwrAreaFile]
FAILED test_error_reporting.py::test_circle_record_header_rejects_a_non_numeric_vnum
6 failed in 1.89s

With the fix: 6 passed in 0.77s. Full suite: 950 passed in 94.76s.

End-to-end, exercising what a CLI would actually print via str(e):

=== case 1: unterminated mob string, what a CLI prints via str(e) ===
   ...\repro.are line 5 col 0 in section mobiles: Unterminated string
=== case 2: SMAUG/SWR file ending in '#' ===
   SmaugAreaFile: parsed cleanly, mobs=OrderedDict()
   SwrAreaFile: parsed cleanly, mobs=OrderedDict()
=== case 3: Circle bare '#' record header ===
   ParseError : ...\broken.wld line 1 col -1: Expected numeric record header, got ''
=== control: a genuine internal error still surfaces its own text ===
   ...\repro.are line 1 col -1 in section mobiles: Error reading section 'mobiles': RuntimeError('internal boom')
=== control: a real area file still parses ===
   test/rom\air.are: 2 mobs 40 rooms 1 objects
   test/rom\arachnos.are: 19 mobs 56 rooms 4 objects
   test/rom\astral.are: 20 mobs 80 rooms 26 objects

ruff check on area_reader/__init__.py reports the same 153 pre-existing errors before
and after; the new test file is clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PQh6Vypbkqk4vnqPUE8yTY