Run CI against local source and use GCC for tests

[Ddiidev]

Motivation

• Ensure CI and docs workflows do not depend on v install Ddiidev.ini endpoint which can be unavailable or blocked.
• Run formatting and tests directly against the checked-out repository to make validation deterministic and local.
• Use the GCC backend for tests to match the requested compilation environment.

Description

• Updated .github/workflows/ci.yaml to checkout the repository, run v fmt -verify ., and execute tests with v -cc gcc -stats test . instead of installing the module and testing the installed path.
• Updated .github/workflows/ci-page-doc.yml to checkout the repository and construct docs with v doc -comments -readme -f html -m . and upload ./_docs instead of moving installed module files.
• Removed steps that relied on v install Ddiidev.ini and on moving ~/.vmodules contents into the workflow workspace.

Testing

• Ran ruby -e "require 'yaml'; %w[.github/workflows/ci.yaml .github/workflows/ci-page-doc.yml].each{|f| YAML.load_file(f); puts \"ok #{f}\"}" which succeeded for both modified workflows.
• Attempted to run v -cc gcc -stats test . but it could not be executed because the v compiler is not installed in this environment.
• Attempted to obtain the V toolchain (via network git clone/downloads) but network/proxy restrictions returned HTTP 403 and prevented installing v, so automated test execution could not be completed here.