Add cosmetic Component archetype axis with palette grouping and archetype-keyed affinity #79

What to build

Introduce archetype — the behavioral family a Component kind belongs to (RelationalDatabase, ObjectStore, MessageQueue, ComputeRuntime, HttpApi, …) — as a new cosmetic facet of NodeKind. Archetype is the single behavioral + grouping axis; there is deliberately no separate category facet (it would be a near-duplicate partition that re-creates the drift the catalog refactor removed). Archetype confers no validation or authorization — it suggests palette grouping now, and (in a later slice) default spec kinds and doc scaffolds.

Scope:

• Add an Archetype union (client-safe, Zod/TS only — never a Prisma enum) and ARCHETYPE_META: Record<Archetype, { group }>, where group is the coarse palette header ("Databases", "Compute", …). ARCHETYPE_META stays lucide-free so it is server-importable later.
• Add a required archetype field to every KindMeta row. "STRUCTURAL" is the honest escape hatch for kinds that are no behavioral family (GENERIC, REGION, MODULE, TABLE, …). Exhaustive both ways: Record<NodeKind, KindMeta> forces every kind to declare an archetype; Record<Archetype, …> forces every archetype to declare its meta.
• Re-key affinity by archetype: change the suggestion map to Record<Archetype | "ROOT", readonly NodeKind[]> plus a small KIND_AFFINITY_OVERRIDE: Partial<Record<NodeKind, …>> that wins when present (for genuine vendor specifics). Affinity values stay concrete kinds (archetypes aren't pickable). The client maps the breadcrumb's kind → archetype before lookup; archetype never goes onto the breadcrumb payload (ADR-0019 payload discipline).
• Palette groups the "All kinds" tail by ARCHETYPE_META[archetype].group; empty groups are dropped during search.

This slice ships only the existing (CORE) kinds — no GCP yet — so it is purely cosmetic regrouping.

Docs travel with the slice: ADR-0034 "Component archetype is a cosmetic facet, not a constraint" (depends-on ADR-0018/0019, amends ADR-0025; carries the explicit "a reviewer tightening this into enforcement regresses this ADR" clause), a new CONTEXT.md "Component archetype" entry (term: archetype, no user/code split), and the "Component kind" drives-list updated to mention palette-group.

Acceptance criteria

• Archetype union + ARCHETYPE_META added (client-safe, lucide-free); every kind declares a required archetype with STRUCTURAL for non-family kinds
• Affinity re-keyed to Archetype | "ROOT" with a per-kind override map; root and per-archetype suggestions verified in dev-browser
• Palette tail renders archetype-grouped headers; empty groups suppressed during search
• ADR-0034 added; CONTEXT.md gains "Component archetype" and updates "Component kind"
• No enforcement anywhere — archetype is read only for presentation/suggestion
• pnpm check and pnpm test green

Blocked by

• Refactor Component-kind catalog into a single KIND_CATALOG record #77