Return SchemaBinary output from a shared arena

[tim-smart]

Summary

• return exact SchemaBinary frame views from a bump-allocated output arena
• isolate active and nested writers so later encodes never overwrite published ranges
• document shared-buffer and transfer behavior, with lifetime, rollover, composition, and concurrent-fiber coverage
• compare arena output with an immediate ownership copy across every existing benchmark case

Verification

• nix develop -c pnpm vitest run packages/effect/test/unstable/encoding
• nix develop -c pnpm lint
• nix develop -c pnpm check
• nix develop -c pnpm --dir packages/effect exec node benchmark/schema/SchemaBinary.ts

The measured arena encode was 4% faster than the copy control for the small record and 1-6% faster for the other cases.

Stacked on #7366 at b64f76655.

Closes EFF-779

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Latest commit: b717e74

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This PR includes changesets to release 30 packages

Name	Type
effect	Major
@effect/opentelemetry	Major
@effect/vitest	Major
@effect/ai-anthropic	Major
@effect/ai-openai-compat	Major
@effect/ai-openai	Major
@effect/ai-openrouter	Major
@effect/atom-react	Major
@effect/atom-solid	Major
@effect/atom-vue	Major
@effect/platform-browser	Major
@effect/platform-bun	Major
@effect/platform-deno	Major
@effect/platform-node-shared	Major
@effect/platform-node	Major
@effect/sql-clickhouse	Major
@effect/sql-d1	Major
@effect/sql-libsql	Major
@effect/sql-mssql	Major
@effect/sql-mysql2	Major
@effect/sql-pg	Major
@effect/sql-pglite	Major
@effect/sql-sqlite-bun	Major
@effect/sql-sqlite-do	Major
@effect/sql-sqlite-node	Major
@effect/sql-sqlite-react-native	Major
@effect/sql-sqlite-wasm	Major
@effect/doctest	Major
@effect/openapi-generator	Major
@effect/docgen	Major

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