enhance(#3913): docs, and the guards come down (#3994)

ADR-3889 terminal phase. Generated docs/reference/exit-codes.md from the exit-code declaration with a --check drift arm; deleted the inert soft-error-exit-zero oracle; promoted untyped-success from SMELL to VIOLATION so it can fail a build; pruned all 5 smell-baseline entries.

Fixed inline: two mis-scoped oracles (routing-validity, value-hygiene), a second source behind the band table, unescaped declaration strings reaching Markdown, and a pre-existing Windows 8.3 short-name path-comparison defect.

Guard ledger corrected from a claimed net -4 to a measured net -1.

Closes #3913

docs/README.md

@@ -95,6 +95,7 @@ Language versions: [English](README.md) · [Português (pt-BR)](pt-BR/README.md)
 - [Review and verification capabilities](reference/review-verification-capabilities.md) — code review, security, and Nyquist capability ownership and hook contracts
 - [Gate predicates](reference/gate-predicates.md) — canonical specification of the phase-gate predicate vocabulary
 - [Capability matrix](reference/capability-matrix.md) — generated catalogue of every capability's role, tier, extension points, hook kinds, and `engines.gsd`
+- [Exit code reference](reference/exit-codes.md) — generated catalogue of every registered process exit code, its name, meaning, and owning module, plus the reserved bands and the v1/v2 exit contract
 - [Capability manifest](reference/capability-manifest.md) — the full `capability.json` schema and validation rules
 - [`gsd capability` command](reference/gsd-capability-command.md) — install / update / remove / list reference for third-party capabilities
 - [Workflow fragments](reference/workflow-fragments.md) — in-file `<!-- gsd:section -->` marker grammar for fragmentizing workflow markdown at emission time