feat: solve issues #9 and #10 (typo tolerance + neighbor-aware embeddings)

[Djain912]

Summary

This PR completes issues #9 and #10 in one batch:

1. Issue Typo tolerance via Levenshtein distance #9: Typo tolerance for lexical matching

• Adds Levenshtein-based typo bonus for edit-distance-1 token pairs.
• Includes length guards and bonus cap to prevent over-boosting.
• Adds focused typo tests and a typo benchmark case.

2. Issue Neighbor-aware embeddings for contextual disambiguation #10: Neighbor-aware embeddings

• Adds immediate-neighbor context blending for embedding vectors.
• Introduces configurable neighbor context weight with clamping to [0, 1] and default 0.10.
• Exposes public constructor for configurable weight.
• Adds disambiguation tests and benchmark comparison with context disabled.

API

• Added:
  • NewEmbeddingMatcherWithNeighborWeight(e Embedder, weight float64) ElementMatcher

Files

• docs/reference/api.md
• internal/engine/benchmark_test.go
• internal/engine/embedding.go
• internal/engine/embedding_test.go
• internal/engine/lexical.go
• internal/engine/lexical_test.go
• semantic.go
• semantic_test.go

Validation Performed

• go test -count=1 ./...
• go test ./internal/engine -run "TestLexicalScore_TypoTolerance_RealWorldSettings|TestEmbeddingMatcher_NeighborContextDisambiguatesRealWorldButtons|TestEmbeddingMatcher_SingleElement_WithNeighborWeight" -count=1
• go test ./internal/engine -run ^$ -bench . -benchtime=1x
• Manual CLI checks on real snapshots:
  • go run ./cmd/semantic find "login button" --snapshot testdata/snapshots/login-page.json --top-k 3 --format table
  • go run ./cmd/semantic find "add to cart" --snapshot testdata/snapshots/ecommerce-product.json --top-k 5 --format refs
  • go run ./cmd/semantic match "add to cart" e10 --snapshot testdata/snapshots/ecommerce-product.json
  • go run ./cmd/semantic classify "node is detached from document"

Environment Notes

• go test -race ./... could not run on this Windows environment due local cgo/compiler limitation.
• bash scripts/check.sh and bash scripts/e2e.sh could not run because WSL is not installed on this machine.

Closes #9
Closes #10