perf(table): resolve only requested equality-delete field paths

[fallintoplace]

Summary

• Resolve less: Equality-delete setup now resolves only field IDs from the active delete sets.
• Reuse traversal state: Internal schema fields are borrowed for the read-only walk, and only matching paths are copied.
• Keep validation: Existing nested paths and ambiguous-column errors remain covered.

Benchmark

Apple M1 Pro, Go 1.26.3, 2,048-field schema:

• 1 equality field: about 586 KB / 4,128 allocs to 672 B / 7 allocs
• 8 equality fields: about 586 KB / 4,128 allocs to 896 B / 21 allocs
• 1-field setup time: about 280 us to 10 us

Tests

• go test -timeout=5m across all packages except io/gocloud
• go test -race -timeout=5m . ./table/...
• golangci-lint run --timeout=10m