v0.9.14: notebook_read/notebook_edit for .ipynb (cell-level)

Source: tool-surface survey 2026-09-15. Zero `ipynb|notebook|jupyter` hits in the tree; pandoc's conversion is lossy one-way.

Claude Code ships NotebookRead/NotebookEdit; prime-agent ships a Jupyter kernel. Codewhale ships a `finance` tool and `validate_data` — the data/quant user story is clearly real, and that audience lives in notebooks.

## Proposal

`notebook_read` / `notebook_edit` for `.ipynb` — cell-level read and replace, standard bounded scope.

Search the tree for the existing tool-surface and pandoc conversion entry points; the survey reports no current ipynb, notebook, or jupyter hits. Define the bounded cell-level read and replace behavior for .ipynb files, then verify that the proposed tools support the notebook workflow without relying on lossy one-way conversion.

Written by the indexing model from the issue text.