Add pass-through result to ROT13 Brute Force

[zhangli091011]

Description

Include the unmodified input as Amount = 0 in the ROT13 Brute Force output.

This allows the operation to be chained with other brute-force operations without discarding candidates that do not require a rotation at the current step.

The pass-through uses amount zero rather than amount 26 because rotating numbers by 26 would not be a no-op.

Existing Issue

Fixes #2437

Screenshots

Not applicable. This change does not modify the UI.

AI disclosure

OpenCode was used to assist with repository analysis, implementation, and test preparation. The resulting changes and test results were reviewed locally.

Test Coverage

Added regression tests covering:

• the Amount = 0 pass-through result
• letter and number pass-through behavior
• sample offset and sample length handling
• crib filtering
• output with Print amount disabled

Validation performed with Node.js 24.18.0:

• npm test: 262 Node API tests and 2,243 operation tests passed
• npm run lint: passed with one pre-existing warning in FromDecimal.mjs
• npm run node: passed
• targeted ESLint: passed
• git diff --check: passed

The production Webpack build was attempted but is currently blocked on Windows by existing Jimp and BMFont loader errors unrelated to this change.

[CLAassistant]

All committers have signed the CLA.