feat(kernel): split runtime modules and add transport/rollback checks

[vaddisrinivas]

Summary

• Split kernel runtime concerns into focused modules for computed values, operations, security, and workflow helpers.
• Route data-home transport through HTTP adapter-safe path (no Metro-incompatible Node SDK imports).
• Add regression and platform gates: chat send + rollback-idempotency tests, shell-route/computed/operations/widget-primitives/workflow tests.
• Add temporary 12k kernel-size guard with explicit README note and 11.8k LOC status; 10k target deferred.
• Keep changes scoped to platform/runtime/tests/workflow plus docs and workflow files.