[tannerpolley]

Summary

Adds native Run cell, Run all, Interrupt, Restart and Save to workspace notebook previews. The optional fork wrapper uses destination-environment T3 RPC and the existing sanitized renderer; unconfigured projects and attachments retain static viewing.

file tree / workspace artifact → trusted notebook identity → server document subscription
                                                        → run / save / recovery controls

Closes #212

Evidence

• Codex checker accepted 778389588ef60a75ba9ff5833538488e7a1e6685. The real RPC subscription regression covers successful values while waiting, live deltas, disconnection and generation recovery. Other regressions cover active-run identity during late output, artifact/worktree routing, and discarding older notebooks without writing disk.
• 162 changed-file tests pass across ten files; format, lint and GraphQL pass. Server, web, contracts and client-runtime typechecks pass. The overall changed-file gate retains established baseline mobile type and Knip failures.
• Owner-authorized integrated Browser panel pass used isolated development state and a local test Jupyter server: static fallback created no kernels; Run showed stdout 42; Save persisted stdout and count; reconnect retained results; restart showed previous-kernel provenance; dirty close offered Save/retain/discard and retained the draft. Test servers stopped, zero kernels remained, and the temporary notebook/token were removed. Initial interpreter mismatch was rejected until the trusted test profile matched the actual interpreter. Existing discovery produced ancillary kernel diagnostics in this dev run; they were not used as result evidence.
• After merging current main without conflicts: server, web, contracts and client-runtime typechecks passed again, plus 79 affected tests across six files.
• Before/after screenshots are uploaded to GitHub evidence as SVG wrappers containing the original PNG captures, without repository assets.

Merge Danger

Door: Two-way

Blast Radius: Viewer

Desktop inherits web behavior. Mobile and agent MCP tools remain outside this phase. Notebook documents keep one service writer; discard is protected, revision-checked reload rather than a filesystem write.

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