[tannerpolley]

Summary

Adds the optional server foundation for running workspace notebooks through a configured loopback Jupyter Server. Notebook-owned modules retain lossless documents, own kernels, correlate executions, and publish bounded snapshots and deltas through typed, authorized fork RPCs.

Fork RPC → NotebookService → JupyterTransport → loopback Jupyter
                ↓                 ↓
       document + run owner   bounded message admission

Execution remains disabled in production composition until trusted configuration is supplied. Persistence/lifecycle, viewer controls and agent tools follow in #211–#213.

Closes #210

Evidence

• Independent Codex checker accepted d5739bd76db1f62a947efd27675dfd0f7454eb4a after regression checks for generation fencing, cleanup retry, per-notebook locks, canonical ownership, bounded completion and output-loss attribution.
• Before: valid aborted replies disconnected. After: actual-frame tests pass in both reply/idle orders; provenance retains the status, remaining cells do not run, and no error output is invented.
• 52 focused tests pass; the changed-file gate passes formatting, lint, GraphQL and 65 tests. Contracts typecheck passes. Server typecheck has two independently confirmed baseline MCP SDK import errors; the overall changed-file gate also retains baseline mobile type and unused-code failures.
• After merging current main without conflicts: contracts and server package typechecks and 63 affected tests passed. Dependencies were refreshed from the frozen lockfile. Current main fixes the previously reported MCP SDK import errors; the broader baseline mobile/unused-code findings remain disclosed above.
• Real local Jupyter execution verified arithmetic, large source/error payloads, visible oversized-output loss, interrupt, restart/state reset, and cleanup to zero owned kernels. Only captured launch PIDs were stopped.
• Binary kernel frames are explicitly unsupported. No browser, dev server, T3 installation, restart or release was performed.

Merge Danger

Door: Two-way

Blast Radius: Server

New optional fork RPC/contracts and notebook modules; no database migration or automatic execution on open.

Implemented and reviewed with Codex GPT-6.1 Sol through T3 Code's Codex harness.