Document minimum wrapcol of 2 for a85encode with adobe=True

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: The a85encode docstring states: "If wrapcol is non-zero, insert a newline (b'\n') character after at most every wrapcol characters."

Expected: Document that adobe=True uses an effective wrapcol of at least 2; retain intact Adobe delimiters.

Actual: b'<\n>' has two lines of length 2 despite wrapcol=1.

import base64

b, wrapcol = b'', 1
if not isinstance(b, bytes) or not isinstance(wrapcol, int) or wrapcol <= 0:
    print("REFUTATION REJECTED: invalid input")
else:
    actual = base64.a85encode(b, wrapcol=wrapcol, adobe=True)
    raw = b'<~~>'  # Empty payload, independently framed with Adobe markers.
    expected = b'\n'.join(raw[i:i + wrapcol] for i in range(0, len(raw), wrapcol))
    if any(len(line) > wrapcol for line in actual.split(b'\n')):
        print("REFUTATION CONFIRMED:", (b, wrapcol), "actual:", actual, "expected:", expected)
    else:
        print("REFUTATION REJECTED: every line satisfies wrapcol")

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library base64:

REFUTATION CONFIRMED: (b'', 1) actual: b'<~\n~>' expected: b'<\n~\n~\n>'

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/base64-20261003-020052-c3

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).