Rebrand Puppet/Facter -> OpenVox/OpenFact in docs and comments

[silug]

Short description

Rebrand user-facing product references, following the treatment of OpenVoxProject/openvox#530:

• Facter -> OpenFact and Puppet -> OpenVox in README, Extensibility.md, docs/data-flow.md, code comments, docstrings, the --puppet CLI option description, fact schema descriptions, and log/warning message text (plus the matching spec expectation)
• puppet-agent -> openvox-agent where the AIO package is meant in prose
• Rewrite puppet.com documentation links to docs.openvoxproject.org
• Point CONTRIBUTING.md at the OpenVoxProject contribution documents
• Update author/email/homepage packaging metadata in ext/project_data.yaml to the OpenVox Project, matching openfact.gemspec
• Regenerate the man page with rake gen_manpages

Deliberately unchanged: the facter executable and man page command name, Facter/LegacyFacter Ruby namespaces and API, fact and resolver names, environment variables, file paths, registry keys, references to the Puppet language/DSL and manifests, comparisons with upstream Facter releases (Facter 3/4), copyright and license attributions, and CHANGELOG/HISTORY entries.

Generated by Claude Code

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
• read and accepted the AI Policy document and added Generated-by or Assisted-by annotations to each of my commits created with the help of an AI agent
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)