fix(memory): handle punctuation and whitespace in extractWords

[koriyoshi2041]

Summary

Fixes #569.

extractWords in memory/inmemory.go currently splits text only on spaces (strings.SplitSeq(text, " ")), which means:

• Words separated by tabs or newlines are not properly tokenized
• Punctuation attached to words (e.g., "great!", "banana,") prevents keyword matching

Changes

• Replace strings.SplitSeq(text, " ") with strings.Fields(text) to handle all Unicode whitespace (tabs, newlines, multiple spaces)
• Add strings.TrimFunc to strip non-letter/non-number characters from word boundaries
• Add 3 test cases covering punctuation, multi-line text, and comma-separated values

Test plan

• go test ./memory/ -run Test_inMemoryService_SearchMemory — all 8 tests pass (5 existing + 3 new)
• go vet ./memory/ — clean

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[hyangah]

Can you keep using strings.SplitSeq? That avoids unnecessary allocation.

[koriyoshi2041]

Good point! Switched to strings.FieldsSeq which gives us the iterator (no slice allocation) while also splitting on all unicode whitespace (tabs, newlines, etc.) — best of both worlds.

[koriyoshi2041]

Rebased this onto current main and cleaned up the gofmt alignment in the added memory tests. The change still uses strings.FieldsSeq, so it keeps the iterator/no-slice-allocation path from your review note while handling punctuation and other whitespace.

Checked locally:

go test ./memory
go test -race -mod=readonly ./memory
go vet ./memory
git diff --check