Strengthen fixture coverage and simplify validation commands

[GsCommand]

Motivation

• The v1.1.0 example surface contained copy-paste contaminated invalid fixtures (wrong verb, identical toy failures and placeholder hashes) that undermined validation credibility.
• The goal was to make examples intentional: realistic valid receipts, single-failure invalid request coverage, and an unambiguous validation command topology so a new contributor can trust and run validation quickly.

Description

• Replaced and expanded the entire JSON fixture set under examples/v1.1.0/commons/*/json/{valid,invalid} to provide per-verb disciplined coverage (minimal + richer valid requests, canonical ok+error receipts, and targeted invalid cases such as missing-verb, missing-input, empty-input, invalid-version, extra-property, invalid-mode, wrong-input-type, and explicit wrong-verb-literal cases). Representative files: examples/v1.1.0/commons/*/json/invalid/001-missing-verb.request.invalid.json and */json/valid/900-ok.receipt.valid.json.
• Made valid receipts look operationally credible by using well-formed sha256: digests, CID-shaped result_cid values, and realistic example detached signatures (replaced 1111.. placeholders).
• Simplified validation command topology in package.json so npm run validate is the single top-level command, with two distinct subcommands kept: validate:schemas and validate:examples; removed the redundant ajv-run.mjs convenience alias.
• Hardened scripts/validate-examples.mjs to be deterministic and more diagnostic: deterministic file sort, explicit detection of request vs receipt files, per-file AJV error formatting, per-verb and per-version summary counts, and safer schema preloading.
• Updated contributor docs (README.md, ONBOARDING.md) to describe the canonical workflow and added a concise Fixture discipline section that records rules for realistic valid examples and targeted invalid fixtures.
• Files changed (representative): package.json, scripts/validate-examples.mjs, README.md, ONBOARDING.md, deletion of scripts/ajv-run.mjs, and all JSON fixtures under examples/v1.1.0/commons/*/json/{valid,invalid} (173 paths touched in the commit).
• No schema edits were required; existing v1.1.0 schemas validated all new fixtures as intended.

Testing

• Ran npm run validate:schemas and all schemas compiled successfully (45 schemas compiled).
• Ran npm run validate:examples and the new v1.1.0 fixture matrix passed; summary printed per-verb/per-version totals (example output included per-verb counts).
• Ran npm run validate (full pass) and it completed successfully (schema compile + examples verification).
• Ran a small Python verification to count fixtures and assert no unintentional cross-verb wrong-verb literals; results: v1.1.0 totals = 40 valid (20 requests, 20 receipts) and 100 invalid (80 requests, 20 receipts) and no accidental wrong-verb mismatches.

Notes on scope and remaining gaps

• No protocol semantics were invented; request schemas are intentionally flat in v1.1.0 so coverage focuses on scalar/boundary behaviors; nested-object validation will require schema changes when semantics demand them.
• The repo now demonstrates intentional fixtures, realistic receipts, and a clear validation workflow so a skeptical protocol engineer can reproduce and trust the validation surface.

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Codex Task