Tighten validation and release metadata hygiene

[GsCommand]

Motivation

• Eliminate duplicated/contradictory JSON parsing helpers and make strict JSON loading canonical and predictable.
• Remove misleading schema-framing and ambiguous alignment metadata so metadata reflects declarative, not enforced, claims.
• Harden release/readiness tooling and provenance wording so checksum and packaging behavior is clear to integrators.

Description

• Canonicalize strict JSON loading by removing inline duplicate-key detectors and switching validation scripts to import and use loadJsonStrict from scripts/load-json-strict.mjs.
• Treat schemas/v1.1.0/index.json as an inventory artifact (removed $schema and $id, adjusted schemas_root to a path), and make validators reject decorative schema framing on that file.
• Remove redundant explicit schemas/v1.1.0/index.json entries from checksum TARGETS in scripts/generate-checksums.mjs and scripts/validate-integrity.mjs while preserving recursive coverage of schemas/v1.1.0/; regenerate checksums.txt.
• Soften manifest alignment metadata by renaming aligns_with to declared_alignment and require the declarative field in validation rather than implying CI-enforced alignment.
• Remove vestigial tsconfig.json to avoid contradicting documented no-TypeScript teaching surface.
• Clarify checksum trust limitation in provenance docs by adding an explicit sentence that checksum validation confirms covered files relative to the checked-in checksums.txt ledger but does not independently authenticate that ledger; applied to SECURITY_PROVENANCE.md, INTEGRATOR.md, and README.md.
• Add release-boundary follow-through: add `

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Codex Task