Remediate Envguard for a verified first release

[1337lean]

What changed

• make explicit schema failures fatal and validate schemas before environment input
• reject non-finite numbers and enforce a documented type/constraint matrix
• propagate human and JSON report writer failures
• add native CI, Staticcheck, vulnerability scanning, CodeQL, and full release validation
• build once, verify all six archives, attest the verified bytes, then publish

Root cause

The initial implementation treated any missing schema like optional auto-discovery, accepted non-finite parsed floats, and did not distinguish irrelevant schema constraints or failed report writes. The release job also published before checking one archive.

Validation

• go test ./...
• go test -race ./...
• go vet ./...
• Staticcheck v0.7.0
• govulncheck v1.1.4
• Actionlint v1.7.12
• GoReleaser v2.17.1 check and six-target snapshot
• independent checksum/content/architecture/native-smoke validation

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