Improve marimo-pair invocationMessage

[manzt]

As code is executing via the marimo_executeCode tool, we can provide a high-level "invocation message" which summarizes the action in the kernel. We could maybe use a language model to summarize this in the future, but this is a simple first step.

[Copilot]

Pull request overview

Improves the VS Code Language Model Tool invocation spinner message for marimo_executeCode by summarizing what the Python snippet appears to do (particularly when using marimo code-mode context operations), instead of always showing a generic “running code” message.

Changes:

• Added lightweight parsing to detect marimo code-mode context variable(s) (async with cm.get_context() as ctx:) and infer common actions (create/edit/delete/move/run cells, package add/remove).
• Added a summarizer that maps detected actions into short, human-readable phrases (e.g., “Editing and running cells”).
• Updated the tool’s prepareInvocation to use the summarizer output as invocationMessage.

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[github-actions]

Coverage Report

Area	Lines	Branches	Functions
Python	50.15% (545 / 1030)	39.55% (106 / 268)	—
TypeScript	47.88% (2283 / 4768)	39.22% (905 / 2307)	45.50% (627 / 1378)

_{TypeScript statements: 47.56% (2376 / 4995)}