fix: resolve parse errors in selected R scripts

[DiogoRibeiro7]

Description

This PR fixes parse errors in a few existing R scripts without changing their intended behavior.

What changed

• corrected if/else structure in interactive search scripts
• replaced malformed/non-ASCII text that was contributing to parse failure
• fixed a mismatched closing delimiter
• split an invalid combined assignment into valid statements

Verification

Each updated file was checked with Rscript -e 'parse(file=...)'.

[Copilot]

Pull request overview

Fixes an R parse error in the interactive example portion of the Z-algorithm pattern search script by correcting the if/else block syntax.

Changes:

• Add braces around the if/else block to make it syntactically valid in R.
• Normalize the “Pattern not found” message string.

[siriak]

Looks good, thanks!