feat(web): implement SearchCluster splitting 🚂

[jahorton]

This PR serves to implement SearchQuotientCluster.split() in full, meeting the following criteria:

1. If two or more paths result in an identical left-hand split result, that result should be deduplicated to a single instance.
   - This requires (live) use of the .isSameNode() method from feat(web): add isSameNode for duplicate quotient-node detection 🚂 #15478, which is designed to identify such cases. It thus is no longer unit-test only.
2. The results must meet the criteria for 'convergence' as described in change(web): track right-hand split index for input source of tokenized transforms 🚂 #15104 - even if that means returning multiple possible split tuples.
   - We must not group left-hand side paths (or right-hand side paths) that represent different subsets of the user's original keystrokes.
3. The SearchQuotientCluster type should be leveraged for results where applicable - where two or more paths converge to the same total subset of keystroke input + codepoint length.

Build-bot: skip build:web
Test-bot: skip

[keymanapp-test-bot]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Web
  • KeymanWeb Test Home - build : all tests passed (no artifacts on BuildLevel "build")

[ermshiperete]

Suggested change

	// and with new spaceIDs.ß
	// and with new spaceIDs.

[ermshiperete]

Is this correct? search-quotient-spur.ts uses

const internalSplitIndex = charIndex - (this.codepointLength - this.insertLength);

so I'm wondering if this should be ?

Suggested change

	const segmentSplitIndex = splitSegment.codepointLength - splitLocation;
	const segmentSplitIndex = splitLocation - (splitSegment.codepointLength - splitSegment.insertLength);