fix: improve runtime placeholder handling

[GordonSmith]

Fixes previous issues with update and remove

Checklist:

• The commit message is properly formatted and free of typos.
  • The commit message title makes sense in a changelog, by itself.
  • The commit message includes a "fixes" reference if appropriate.
  • The commit is signed.
• The change has been fully tested:
  • I have viewed all related gallery items
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• There are no similar instances of the same problem that should be addressed
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  • I have raised new issues to address them separately

Testing:

[Copilot]

Pull Request Overview

This PR improves runtime placeholder handling in the observablehq-compiler package by refactoring the API to better manage cell lifecycle operations. The changes rename functions for consistency and enhance error handling for cell operations.

• Renamed compileKit to compileNotebook for better naming consistency
• Enhanced runtime cell management with improved add/update/remove operations
• Added proper error handling for cell state management

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/observablehq-compiler/tests/index-notebookkit.ts	Updates import and function call to use new compileNotebook name
packages/observablehq-compiler/tests/index-notebookkit.js	Updates import and function call to use new compileNotebook name
packages/observablehq-compiler/src/kit/runtime.ts	Major refactor of cell management methods with better error handling
packages/observablehq-compiler/src/kit/index.ts	Reorders exports
packages/observablehq-compiler/src/kit/compiler.ts	Refactors compilation logic and renames functions
packages/observablehq-compiler/src/index.ts	Updates exports to use new function names
packages/observablehq-compiler/src/compiler.ts	Updates function call to use new compileNotebook name
packages/observablehq-compiler/index-kit.html	Uncomments CSS styles

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[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

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[jeclrsg]

@GordonSmith I didn't have anything to add; couple of pending copilot comments however