Sisco/fix editor replace method

[dsisco11]

Fix Query Region System and SyntaxEditor Replacements

Summary

This PR refactors the entire node query system to fix fundamental issues with how SyntaxEditor handles multi-node replacements and range queries like Query.Between. The core problem was that SyntaxEditor was designed around single-node replacements, but queries can match multiple sibling nodes that need to be replaced atomically.

Problem

The original implementation had several shortcomings:

1. Query.Between and sequence queries match multiple consecutive siblings, but SyntaxEditor.Replace() only handled single-node replacements
2. Block inner queries (.Inner(), .Start(), .End()) didn't correctly resolve to slot positions within the parent
3. Path computation was expensive - NodePath.FromNode() was called in hot loops during region enumeration

Solution

Introduced a new QueryRegion abstraction that represents a contiguous range of slots within a parent container:

internal readonly struct QueryRegion
{
    public NodePath ParentPath { get; }      // Path to parent container
    public int StartSlot { get; }            // First slot index (inclusive)
    public int EndSlot { get; }              // Last slot index (exclusive)  
    public SyntaxNode? FirstNode { get; }    // First node in range (for trivia)
    public int Position { get; }             // Document position
}

This allows SyntaxEditor to correctly:

• Replace ranges of nodes atomically (e.g., Query.Between(start, end))
• Handle zero-width insertion positions (e.g., empty block inner)
• Insert at specific slot positions within containers

Key Changes

New Files:

• QueryRegion.cs - Region struct and IRegionQuery interface
• PathTrackingWalker - O(1) incremental path tracking during tree traversal
• SyntaxEditorBenchmarks.cs - Comprehensive benchmarks for editor operations

Modified Files:

• SyntaxEditor.cs - Rewritten to use regions instead of single nodes
• NodeQueryTypes.cs - Added IRegionQuery implementations to all query types
• QueryCombinators.cs - Updated combinators to produce correct regions
• GreenNode.cs - Added GetLeadingTrivia/TrailingTrivia and GetFirstLeaf/GetLastLeaf helpers
• GreenBlock.cs - Added slot-based child access methods

Performance Optimizations

1. PathTrackingWalker - Tracks path incrementally during traversal (O(1) per step vs O(depth) for NodePath.FromNode())
2. Lazy ParentPath - Only computed when actually accessed during editing
3. Precomputed trivia widths - Uses GreenLeaf.LeadingTriviaWidth/TrailingTriviaWidth instead of summing at runtime
4. Optimized SelectRegions - Inlined match checks for KindNodeQuery and BlockNodeQuery

Test Coverage

Added 15+ new tests covering:

• Query.Between with Replace/Remove/Insert/Edit operations
• Block inner content replacement (empty and non-empty)
• Multi-position insertions (50+ positions)
• Deep tree traversal (20-50 levels)
• Trivia preservation across edits

Breaking Changes

None - all changes are internal. The public SyntaxEditor API is unchanged.

Files Changed

 SyntaxEditorBenchmarks.cs     | 375 ++++++++++++++
 SyntaxEditorTests.cs          | 362 +++++++++++++
 QueryRegion.cs                | 245 +++++++++
 SyntaxEditor.cs               | 572 ++++++++++++---------
 NodeQueryTypes.cs             | 286 +++++++++++
 QueryCombinators.cs           | 181 +++++++
 GreenNode.cs                  |  88 ++++
 GreenBlock.cs                 | 203 ++++++++
 17 files changed, 2388 insertions(+), 739 deletions(-)