Fix Python receipt and verb extraction regressions (PR #36)

[GsCommand]

Motivation

• Restore the intended Commons contract so ordinary (non-commercial) requests do not carry x402 metadata while commercial/payment envelopes do.
• Repair receipt verification so verify_receipt returns ok=True for the provided canonical fixture receipt_valid.json by not forcing metadata.receipt_id to equal the proof hash.
• Ensure extract_receipt_verb returns the canonical verb when present and falls back to legacy heuristics from result shapes for older fixtures.
• Keep lint/formatting changes (imports/line wrapping) and retain strict type checks.

Description

• Removed x402 emission from build_commons_request and added x402 into build_commercial_request so metadata is present only for commercial flows (python-sdk/commandlayer/client.py).
• Updated extract_receipt_verb to prefer receipt.verb, then x402.verb, then legacy result-based heuristics (e.g. result.summary -> "summarize") to recover expected verb extraction for legacy fixtures (python-sdk/commandlayer/verify.py).
• Changed receipt verification logic so receipt_id_matches treats metadata.receipt_id as opaque (no equality requirement with proof.hash_sha256) while preserving hash/signature/canonical checks, restoring successful verification for receipt_valid.json (python-sdk/commandlayer/verify.py).
• Made defensive casts and small refactors to satisfy lint/type tooling and normalized legacy runtime-shaped responses via normalize_command_response (python-sdk/commandlayer/client.py, python-sdk/commandlayer/verify.py).
• Adjusted unit test expectation to reflect commons request contract (python-sdk/tests/test_public_api.py) and kept other existing tests intact.

Testing

• Ran linting: cd python-sdk && python -m ruff check . — passed.
• Ran static types: cd python-sdk && python -m mypy commandlayer — passed.
• Ran unit tests: cd python-sdk && python -m pytest tests/ -v — all tests passed (25 passed, 1 warning).
• Ran parity check: node scripts/parity-check.mjs — failed due to TypeScript-side parity/build issues (DTS/type errors and an unrelated receiptIdPresent/naming mismatch in the TypeScript build), which are independent of the Python fixes.

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Codex Task