Extract ScriptInfo and DocumentRegistry to common container

[andrewbranch]

This is a minor refactor that will make it easier to share files/state between LSP, MCP, and the IPC API.

[Copilot]

Pull Request Overview

This PR refactors the code by extracting the ScriptInfo and DocumentRegistry logic into a common container called DocumentStore, in order to share state among LSP, MCP, and the IPC API.

• Removed multiple fields (documentRegistry, scriptInfos, and related locks) in favor of a single DocumentStore.
• Updated methods in Service and API to delegate functionality to the DocumentStore.
• Introduced a new DocumentStore file to encapsulate the shared logic.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
internal/project/service.go	Replaced direct management of ScriptInfo with calls to DocumentStore.
internal/project/documentstore.go	Introduced DocumentStore for handling ScriptInfo and DocumentRegistry.
internal/api/api.go	Updated API to delegate document and script info operations to DocumentStore.

[jakebailey]

Seems fine as a refactor, but I am increasingly unsure about our model here; I would really like to reformulate all of this as a real snapshot model so we can entirely eliminate all of the weird races that come from trying to manage the registry, updating script infos, etc...