wave.open raises EOFError instead of wave.Error for a truncated fmt chunk

Bug description

wave.open(f, 'rb') is documented to raise wave.Error when a file violates
the WAV format, but it leaks a raw EOFError when the fmt chunk is truncated
(the chunk header declares 16 bytes but fewer are present):

>>> import io, struct, wave
>>> b = b'RIFF' + struct.pack('<L', 24) + b'WAVE' + b'fmt ' + struct.pack('<L', 16) + struct.pack('<HHLLH', 1, 1, 11025, 11025, 1)
>>> wave.open(io.BytesIO(b))
Traceback (most recent call last):
  ...
EOFError

Expected: wave.Error. Wave_read._read_fmt_chunk() raises EOFError on a
short read, but Wave_read.initfp() does not wrap that call, so it escapes the
public API. Every other malformed-input path in the module raises wave.Error.

CPython versions tested on

3.13, 3.14, 3.15

Operating systems tested on

Linux, macOS

Linked PRs

• gh-153693

Start at wave.open and inspect Wave_read.initfp() and Wave_read._read_fmt_chunk(), which the report identifies as the relevant entry points. Add a regression check for a truncated fmt chunk and verify that malformed input raises wave.Error rather than EOFError; gh-153693 is already linked to this work.