Add module entrypoint and release smoke-test guidance for pre-0.1.0 hardening

[srichs]

Motivation

• Provide a reliable fallback invocation path and enable a simple smoke test for packaged artifacts before cutting 0.1.0.
• Ensure the release checklist includes explicit artifact build/install verification to catch packaging/runtime regressions early.
• Surface prioritized pre-release hardening steps in the project review to guide final release work.

Description

• Add a module entrypoint at src/devr/__main__.py so users can run python -m devr as a fallback invocation path.
• Add a CLI test in tests/test_cli.py that verifies python -m devr --version works from a source-checkout context.
• Update README.md to include python -m devr --version in the command list and add build/install smoke-test steps to the release checklist.
• Add a short 0.1.0 pre-release additions section to REVIEW.md calling out the module entrypoint, artifact smoke tests, and changelog/version reconciliation.

Testing

• Ran the full test suite with pytest -q and all tests passed (93 passed).
• The newly added test_module_entrypoint_supports_version_flag in tests/test_cli.py was executed as part of the suite and succeeded.

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Codex Task