Fix multi-version documentation to show correct version numbers

[david-tingdahl-nvidia]

Problem

When building multi-version documentation with sphinx-multiversion for
branches v0.0.8-docs and v0.0.9-docs, both versions incorrectly displayed
"nvblox_torch 0.0.9" in the page titles and all wheel download URLs pointed
to v0.0.9 files, regardless of which version was being built.

Root Cause

Multiple interacting issues:

1. Python Module Caching: The original approach imported version from setup.py at module level. Python's import system cached the first imported module, causing all subsequent builds to reuse the same cached version (0.0.9) across all versions.

2. Timing Issues: conf.py is executed before sphinx-multiversion sets up version-specific source directories, so CWD-based detection failed.

3. Config Dictionary Creation: The nvblox_torch_docs_config dictionary was created at module import time with hardcoded/default version values, before the correct version could be detected.

Solution

Use Sphinx's setup() function which runs after initialization and provides
app.srcdir pointing to each version's checked-out source directory.

The setup() function:

1. Detects the version by reading setup.py from app.srcdir (the correct version-specific checkout directory)
2. Updates app.config.html_title with the correct version
3. Updates app.config.nvblox_torch_docs_config with version-specific:
   • external_wheel_base_url (e.g., /download/v0.0.8/ vs /download/v0.0.9/)
   • wheel_name_* entries with correct version and patch (rc5 vs .dev1)

Changes

docs/conf.py (both v0.0.8-docs and v0.0.9-docs):

• Removed module-level version import from helpers.py/setup.py
• Set NVBLOX_VERSION_NUMBER to default value (overridden in setup())
• Added setup(app) function that:
  • Detects version from app.srcdir/nvblox_torch/setup.py
  • Updates html_title dynamically
  • Updates nvblox_torch_docs_config dictionary entries
• Added get_wheel_name() helper function (v0.0.9-docs)
• Added _get_wheel_name() nested function (v0.0.8-docs)
• Changed smv_branch_whitelist from v0.0.8|v0.0.9 to v0.0.8-docs|v0.0.9-docs

docs/_templates/versioning.html (v0.0.8-docs):

• Created version selector sidebar template for sphinx-multiversion

docs/helpers.py (v0.0.9-docs):

• Added get_version_from_multiversion_env() function (initially, later unused)
• Added _read_version_from_setup() with CWD-based detection (later unused)
• Note: These are not actively used in final solution but remain for reference

Results

Each version now correctly displays:

v0.0.8-docs:

• Title: "nvblox_torch 0.0.8"
• Wheel URL: download/v0.0.8/
• Wheel filename: nvblox_torch-0.0.8rc5+cu12ubuntu24-py3-none-linux_x86_64.whl

v0.0.9-docs:

• Title: "nvblox_torch 0.0.9"
• Wheel URL: download/v0.0.9/
• Wheel filename: nvblox_torch-0.0.9.dev1+cu12ubuntu24-py3-none-linux_x86_64.whl

Co-Authored-By: Claude Sonnet 4.5 noreply@anthropic.com

[david-tingdahl-nvidia]

will try other/cleaner method