[FEAT]: expose file.export.common_fluids_format_post in the native settings API

[sebastianwidmann]

❓ Problem statement

The Common Fluids Format post-processing export (.cas.post / .dat.post) is only accessible
through the legacy TUI interface. There is no equivalent in the native object-oriented settings
API, making it inconsistent with the rest of the file.export namespace.

PyFluent exposes two related but distinct CFF concepts:

• Solver I/O CFF (.cas.h5 / .dat.h5) — controlled via session.file.cff_files = True,
  already available in the native settings API at ExposureLevel.STABLE.
• Post-processing CFF (.cas.post / .dat.post) — a separate export target for CFD-Post
  and downstream tools, currently accessible only through the legacy TUI.

The only way to export this format today is via the TUI:

session.tui.file.export.common_fluids_format_post(*args)
# Writes result.cas.post and result.dat.post

This bypasses PyFluent's argument validation, type checking, and journaling infrastructure.
Mixing TUI and settings API calls in the same workflow is inconsistent and fragile across
PyFluent versions.

💡 Proposed solution

Expose common_fluids_format_post as a Command in the native settings API under
file.export, consistent with how other export formats in the same group are already handled:

session.file.export.common_fluids_format_post(**kwargs)

The TUI node already exists in the generated tree as file > export > common_fluids_format_post
(confirmed in tui_261.py), so the underlying Fluent functionality is present. The request is
solely for the corresponding entry in the settings API codegen — analogous to the existing
ExposureLevel.STABLE treatment of the solver-I/O CFF variant.

🔀 Alternatives considered

📦 PyFluent version

0.39.0

🌀 Ansys Fluent version

2025 R2 (25.2)

🐍 Python version

3.12

💻 Operating system

Linux

📌 Additional context

No response