(v1) Guard that integration /standard entries never pull arktype

[yamcodes]

This was generated by AI during triage.

Natural continuation of #1199 (Standard Mode packaging). Spun out while closing #1436.

Agent Brief

Category: enhancement
Summary: Add install/bundle isolation checks so each integration's /standard entry never imports or bundles arktype (or @arkenv/core).

Current behavior:
@arkenv/standard and the framework /standard subpaths are designed to be ArkType-free (ADR 0007). Core already has isolation coverage for the standard engine entry. Integrations expose /standard (and Next/Nuxt nested /standard/*) but there is no automated guard that those published entries stay free of arktype / @arkenv/core.

Desired behavior:
CI (or package tests) fails if any published /standard entry for Vite, Bun, Next.js, or Nuxt pulls in arktype or @arkenv/core — via static import graph and/or built dist inspection, matching the spirit of existing core isolation tests.

Key interfaces:

• Published exports maps for @arkenv/vite-plugin, @arkenv/bun-plugin, @arkenv/nextjs, @arkenv/nuxt — every path under /standard (including nested ./standard/*)
• Existing isolation patterns on @arkenv/standard / @arkenv/core (reuse the same approach where possible)

Acceptance criteria:

• Every published /standard (and nested /standard/*) export for vite-plugin, bun-plugin, nextjs, and nuxt is covered by an isolation check
• The check fails if the entry's module graph or built artifact references arktype or @arkenv/core
• Default (ArkType) entries are not required to pass this check
• Tests run in CI for the affected packages

Out of scope:

• Changing packaging strategy (already done in Distribution: Implement Standard Mode Packaging Strategy (Split core into @arkenv/core and @arkenv/standard) #1199)
• ImportMetaEnvAugmented / ProcessEnvAugmented Standard Mode typing ((v1) Adopt the env object as the canonical surface for Vite/Bun (transform design) #1105)
• Adding Standard Mode examples/playgrounds (separate follow-up)

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[yamcodes]

This was generated by AI during triage.

Note: Out-of-scope line about ImportMetaEnvAugmented / ProcessEnvAugmented was too strong — #1105 keeps SPA-mode ambient helpers. That work is tracked in #1440, still separate from this isolation ticket.