(tree) Update chunking algorithm to use polymorphic shape for incremental fields

[agarwal-navin]

Currently, fields that are specified as incremental via the shouldEncodeIncrementally callback can be monomorphic causing them to be combined in a uniform chunk with its parent.
This will make the field to not be incrementally summarized - When incremental summary builder calls ChunkedForest::chunkField for such fields, it will return a new chunk every time causing it to encode the chunk again and not re-using a summary handle for it.

This PR changes the chunking algorithm so that it always uses polymorphic shape for nodes / fields that are specified as incremental. This is done by plumbing the shouldEncodeIncrementally function to the tryShapeFromSchema function which decides the shapes for fields and nodes. If shouldEncodeIncrementally returns true, a polymorphic shape is returned.

AB#41866

[Copilot]

Pull Request Overview

Updates the chunking algorithm to use polymorphic shapes for fields marked as incremental, ensuring proper incremental summarization by preventing monomorphic fields from being combined into uniform chunks with their parents.

• Replaces shouldEncodeFieldIncrementally parameter with IncrementalEncodingPolicy type
• Integrates incremental encoding policy into shape determination logic
• Updates all related functions and interfaces to use the new policy type

Reviewed Changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/dds/tree/src/feature-libraries/chunked-forest/codec/incrementalEncodingPolicy.ts	Defines new IncrementalEncodingPolicy type and default implementation
packages/dds/tree/src/feature-libraries/chunked-forest/chunkTree.ts	Updates tryShapeFromSchema to return polymorphic shapes for incremental fields
packages/dds/tree/src/shared-tree/sharedTree.ts	Updates interfaces and forest configuration to use new policy type
packages/dds/tree/src/feature-libraries/forest-summary/forestSummarizer.ts	Simplifies parameter handling with new policy type
Multiple test files	Updates test code to use new IncrementalEncodingPolicy type