docs: align receipt verb and verification contract language

[GsCommand]

Motivation

• Ensure documentation matches the SDK behavior that the canonical verb is at top-level receipt.verb and that receipt.x402.verb is legacy/commercial fallback only.
• Clarify verification semantics so the recomputed proof hash is compared to metadata.proof.hash_sha256 while metadata.receipt_id is optional compatibility metadata and not required for a successful ok verification.
• Update examples and Quickstart text so Commons examples include the top-level "verb": "summarize" and avoid presenting x402 as the primary contract.

Description

• Updated wording and examples in README.md, QUICKSTART.md, EXAMPLES.md, typescript-sdk/README.md, and python-sdk/docs/verification.md to reflect the canonical verb and revised verification language.
• Replaced references that treated receipt.x402.verb as primary with text explaining receipt.verb is canonical and receipt.x402.verb is a legacy/commercial fallback.
• Revised verification steps to state the recomputed hash must be compared to metadata.proof.hash_sha256, and to document that metadata.receipt_id, when present, is a compatibility/diagnostic check and not a hard requirement for ok.
• Added top-level "verb": "summarize" to canonical receipt examples and changed the Quickstart final bullet to: "Read the verb from receipt.verb. Legacy/commercial payloads may expose receipt.x402.verb as a fallback.".

Testing

• Ran TypeScript package checks in typescript-sdk with npm run typecheck and the TypeScript unit/cli tests with npm test, and the package test suites completed successfully (unit/template/cli smoke all passed).
• Ran Python tests in python-sdk with pytest -q and the Python test suite passed.
• Attempts to run npm commands from the repository root (npm run typecheck / npm test at /workspace/sdk) failed due to a missing root package.json, but package-level automated tests were executed and passed.

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Codex Task