[codex] Add materialized column support

[rmorehig]

Summary

• add t.*().materialized(expression) for ClickHouse/Tinybird materialized column definitions in generated datasource files
• emit MATERIALIZED <expression> in generated datasource schemas
• skip autogenerated JSON paths for materialized columns unless .jsonPath(...) is explicitly set
• improve live build E2E isolation so each build test uses its own Tinybird branch name and surfaces build API errors clearly

Important note

The live E2E attempt against /v1/build showed the current Tinybird backend rejects this syntax with [raw_logs.datasource] MATERIALIZED columns are not supported. Because of that, this PR keeps coverage at the SDK generator/type level until backend/datafile support exists.

Validation

• pnpm vitest run src/schema/types.test.ts src/generator/datasource.test.ts
• pnpm typecheck
• pnpm test:e2e:live (skipped locally because TINYBIRD_E2E_USER_TOKEN / TINYBIRD_E2E_WORKSPACE_ADMIN_TOKEN are not set)