GeezerVison

Closes #141295.

Persist pdb command history when using PyREPL. Load history when the debugger input is initialized and append commands after each input, so a later pdb process can recall them with the arrow keys.

Add PYTHON_HISTORY_PDB to override the history path. Otherwise, use PYTHON_HISTORY with .pdb appended, falling back to ~/.python_history.pdb. Ignore environment overrides under -E and -I.

Add a PTY test that saves commands and recalls them in a second process, and isolate the PyREPL debugger tests with a shared temporary history file. Update the documentation, environment-variable help, and NEWS.

Why a new env var / file instead of using the existing history file?

pdb and the python interactive shell has different commands - the commands executed in pdb may not be executable in the interactive shell. Mixing the history for these might not be the best idea.

Also, code wise, pdb and _pyrepl are using two different readers (because they have different colorization mechanism), so the history living in memory is different. Mixing the two histories in one file is also technically challenging in an unnecessary way.

Validation:

• ./python.exe -m test test_pdb passes.
• The history integration test was also run directly in a terminal, including after another PyREPL test, with an inherited user-history path verified unchanged. The normal class is skipped with this build's libedit backend.
• git diff --check passes.

• Issue: Save pdb Line History Between Runs #141295