Clean up provider parsing, CLI validation, and duplicate tests

[jogibear9988]

Changes

Separate SQL Server, PostgreSQL, and Oracle default-value parsing from catalog reads and share numeric/binary conversions. Numeric SQL NULL defaults now remain null, malformed binary literals are rejected instead of truncated, and PostgreSQL numeric defaults no longer depend on the table name.

Split CLI options from command execution and validate arguments before loading assemblies or opening connections. Preserve exit codes and credential-safe error messages, and consolidate the driver mapping.

Also fix migration-name edge cases, culture-dependent type lookup, unexpanded type templates, and swallowed factory errors. Remove duplicated loader/type registration logic, unnecessary dialect reflection, dead fixtures, and repeated test cases. Route deliberate obsolete-API compatibility tests through a narrowly suppressed test helper; production warnings remain enabled.

Validation

• Solution rebuild: passed (19 remaining production compatibility/complexity warnings).
• Unit tests: 175 passed, zero skipped, including 53 catalog parser cases.
• SQLite tests: 203 passed, zero skipped; two duplicate generic scenarios removed.
• Whitespace check: passed with CRLF endings allowed.

Server-backed database suites were not run locally because Docker is unavailable; the full provider CI matrix is required before merging. See docs/code-cleanup-review.md for details and remaining cleanup areas.

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