Teach enum Field authoring

[raghubetina]

Summary

• Document the supported enum Field boundary, ordered value identity, and ordinal semantics.
• Add a complete schema-valid example plus local-authoring and successful-push evals.
• Refresh capability diagnostics so enum structure is accepted while defaults and Validations remain fail-closed.
• Document reproducible initialized-state handling for server-backed eval runs.

Stack

• Base: Route schema validation without context waste #3
• API counterpart: firstdraft/firstdraft#196
• The generic CLI in Generate Foundation Plan subject IDs cli#4 needs no enum-specific change.

Verification

• sh script/check: 11/11 passing
• npm audit --audit-level=low: 0 vulnerabilities
• gh skill publish --dry-run: passed with the existing license and tag-protection advisories
• The exact enum fixture was accepted by API commit 3282954 and persisted low, medium, high in order with ordinality enabled
• Local max-effort review: approved with no remaining findings

[raghubetina]

Stacked follow-up #5 is now open on top of this branch: #5

It updates the Skill for the Field-default importer in firstdraft/firstdraft#200 and pins the complete server baseline through firstdraft/firstdraft#202. The enum guidance in this PR remains accurate at its API #196 baseline; with the later API slices included, the statement that enum defaults remain a capability gap is superseded. #5 teaches all four tagged default variants, default ownership without a new subject UUID, omission versus literal null, canonical decimal strings, enum-value rename coupling, and recovery evals. It does not change the bundled schema or generic CLI.

[raghubetina]

This slice has landed on main through #6, which integrated the complete reviewed Skill stack. This PR remains the focused review history for enum Field authoring; no implementation was discarded. Closing as superseded by #6.