Restore thin Polaris CLI without CodeGraph

[FaithZL]

Summary

• restore the standard-library-only polaris dispatcher with exactly eight user-facing commands
• vendor the CLI and package metadata with the repository-locked protocol, releasing Polaris 0.1.16 with an adjacent 0.1.15 migration
• update product documentation and cross-platform CI without restoring CodeGraph/provider functionality

Verification

• python3 tests/run_tests.py — 89/89 passed
• python3 -m compileall -q polaris_cli.py scripts tests
• isolated pip install --no-deps --no-build-isolation . smoke test for corona-polaris 0.1.16 and polaris --help
• final whole-branch review and scoped fix re-review completed