Zod v4 schemas, closed error codes and generated JSON Schema for the AXIOM v2 data model (docs/design/v2-architecture.md §2.2, §3.1, §4.2). Zero runtime deps besides zod.

Module	Exports
`digest`	`Sha256HexSchema`, `DigestSchema`, `DigestRefSchema` (`sha256:<hex>`), `toDigestRef`, `digestRefHex`
`path`	`RelPathSchema`, `isValidRelPath`, `relPathIssues` — relative POSIX, NFC, ≤1024, no `..`/`\`/drive/reserved names/`<>:"
`errors`	`ERROR_CODES` tuple, `ErrorCode`, `AxiomError { code, path?, details? }`, `isAxiomError`, `isErrorCode`
`plan`	`PlanSchema`, `PlanArtifactSchema`, `PlanArtifactSourceSchema` (inline/cas/ref/template)
`check`	`CheckRefSchema`, `FindingSchema`, `CheckReportSchema`
`manifest`	`ManifestBodySchema` (JCS-hashed; artifacts/checks sorted+unique by UTF-8 byte order), `ManifestBundleSchema` (blobs ≤ 4 MiB), `compareUtf8`
`profile`	`ProfileSchema`
`apply`	`ApplyResultSchema`, `AppliedFileSchema`, `JournalSchema`, `ErrorCodeSchema`

Naming: schemas end in Schema; inferred types are bare (Plan, ManifestBundle, …); *Input types are the pre-default shape an agent sends. Callers assert on error codes, never message text.

pnpm build:jsonschema regenerates schemas/*.schema.json (draft 2020-12, input shape) — commit them.

Why isolatedDeclarations: false here: every export is a Zod schema whose type is a deeply nested generic; spelling those annotations by hand is unmaintainable and adds no safety. This package is the only one that overrides the base, and its .d.ts is still emitted by tsdown.