feat(cli): restore Better Auth UI scaffold

[olliethedev]

Closes #219.

Restores Better Auth UI as an optional generated companion while preserving the v3 ownership boundary:

• generates auth + account only against an existing application-owned Better Auth endpoint;
• installs the corrected RC4 / Better Auth 1.6.16 declaration-peer cohort;
• emits one browser client and framework-native session refresh for Next.js, React Router, and TanStack;
• keeps backend auth, database/schema, providers, secrets, organization, and other runtime extensions out of the default scaffold;
• adds exact companion/manual-install/optional-adapter documentation;
• enables isolated transactions for Kanban alongside the other atomic writers;
• adds a permanent three-framework packed clean-install/typecheck/build CI gate.

Validation:

• CLI tests: 170/170
• CLI typecheck and build
• packed init, migration/idempotency, and Next.js production build
• packed Next.js, React Router, and TanStack strict consumer builds
• docs build and registry validation
• root lint, typecheck, build, and diff check
• independent Standards and Spec reviews: no findings

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2 Skipped Deployments

Project	Deployment	Actions	Updated
better-stack-docs	Ignored		Aug 31, 2026 11:26pm UTC
better-stack-playground	Ignored		Aug 31, 2026 11:26pm UTC

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T23:33:32.158346Z	6114199	PR opened

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 6114199902

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[chatgpt-codex-connector]

Only advertise routes enabled by the scaffold

When better-auth-ui is selected, the generated overrides enable only account: true and explicitly omit API-key and teams/organization support, but these entries make the init outro label /pages/account/api-keys, /pages/account/organizations, and /pages/account/teams as “Available routes.” Users following that output reach features whose matching Better Auth server/client plugins were never configured; omit the conditional routes from this default metadata or clearly distinguish them from routes actually enabled by the scaffold.

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