Namespace v2 public symbols (#223)

[codeforester]

Fixes #223

Summary

• Rename every v2 public library and launcher helper to the collision-resistant base_bash_libs_* namespace.
• Rename framework-owned globals, environment controls, load guards, and implementation-only holders to BASE_BASH_LIBS_* / __base_bash_libs_*__.
• Remove generic v1 aliases and add clean-loading collision fixtures for application and third-party symbols.
• Publish the complete migration map in docs/v2-symbol-map.md and the mechanical rewrite/check tool in scripts/migrate-v2-symbols.
• Update examples, READMEs, standards, workflow probes, tests, and the changelog for the v2 surface while keeping every public library as one physical .sh file.

Verification

• ./tests/validate.sh
• 479 BATS cases passed, including the namespace and migration contract suite.
• ShellCheck error profile passed.
• Bash 4.2 caller-option, logging, release-guard, and example smoke checks passed.