Decouple HomegrownAdapter schema authority

[Jesssullivan]

Summary

• add explicit HomegrownAdapter schema injection for business/content and booking Drizzle tables
• keep legacy auth-pg schema loading as an optional compatibility fallback
• remove the mandatory tummycrypt_tinyland_auth_pg Bzlmod edge and move @tummycrypt/tinyland-auth-pg out of published dependencies
• bump release metadata to 0.7.8 and refresh generated docs
• document @tummycrypt/tinyland-business-pg as the intended dedicated schema package consumer

Validation

• pnpm install --frozen-lockfile
• pnpm check:release-metadata
• pnpm docs:check via nix develop
• pnpm check
• pnpm lint
• pnpm test:unit
• pnpm test:integration
• pnpm build
• pnpm check:package
• nix develop --command bazel mod graph shows no tummycrypt_tinyland_auth_pg edge
• nix develop --command bazel build //:pkg
• git diff --check

Boundary

This is the scheduling-kit-side schema authority boundary. It does not add a hard dependency on the new business schema package, and it is not an RBE proof. The companion tinyland-inc/tinyland-business-pg authority surface now exists separately for content/booking Drizzle tables.

[Jesssullivan]

Validation refresh for review:

• CI is green: package / resolve-runner, package / validate (20), and package / validate (22) passed; publish jobs skipped as expected on PR.
• Local checks passed in the PR worktree: pnpm install --frozen-lockfile, pnpm check:release-metadata, pnpm test:unit src/adapters/__tests__/homegrown-adapter.test.ts (40 tests), pnpm check, pnpm lint, pnpm build, and git diff --check.
• Review boundary: this makes HomegrownAdapter schema authority injectable and moves tinyland-auth-pg to an optional legacy fallback. It does not publish 0.7.8, register 0.7.8, or update downstream apps to pass schemas yet.

[Jesssullivan]

Operator review: diff adds explicit HomegrownAdapter schema injection, keeps auth-pg as an optional compatibility fallback, removes the mandatory auth-pg Bzlmod edge, and updates 0.7.8 release metadata. PR checks are green. Boundary is clean: this is schema/package authority cleanup, not RBE or remote-executor proof.\n\nGitHub will not accept approval from the PR author account, so this remains blocked on non-author review or an explicit admin merge decision.