Polish README release framing and refresh checksums

[GsCommand]

Motivation

• Make the repository read and present as a finished, Commons-aligned release package by adding a concise badge/header and honest release wording.
• Remove or confirm absence of dead scaffolding artifacts (tsconfig.json, scripts/.gitkeep) and ensure validator JSON loading is consolidated to a single strict loader.
• Restore integrity validation truth by making the checksum ledger match the canonical index file.

Description

• Updated the README opening to a Commons-style release header with a short protocol-branded title, a three-badge row (schemas / CI / license), and an explicit release notice that clarifies releases/v1.1.0.md is a draft for future GitHub Release publication.
• Regenerated checksums.txt so the integrity ledger matches the current canonical schemas/v1.1.0/index.json (changed checksums.txt).
• Verified that tsconfig.json and scripts/.gitkeep are absent and removed no files because they were already not present.
• Confirmed both validator scripts already consolidate JSON loading onto the shared loadJsonStrict helper (no validator code changes were necessary).
• Files changed: README.md, checksums.txt.

Testing

• Ran repository validation and tests: npm run validate and npm test, both completed successfully after updating checksums.
• Executed the validator scripts directly: node scripts/validate-all.mjs && node scripts/validate-examples.mjs && node scripts/validate-integrity.mjs, which succeeded (note: integrity initially failed until checksums.txt was regenerated, after which it passed).
• Verified absence of unwanted scaffold files with test ! -e tsconfig.json && test ! -e scripts/.gitkeep and searched for references with rg -n "tsconfig\.json|scripts/\.gitkeep" ., both confirming no references.
• All automated validation surfaces reported success after the checksum refresh.

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Codex Task