Consolidate remaining validated robustness fixes

[krotname]

Summary

• consolidate the remaining validated CLI/input-hardening changes
• fix all open review findings: overflow-safe parsing, bounded aggregate search work, CR/CRLF handling, exact deque semantics, canonical Roman numerals, and strict resistor input
• share checked unsigned parsing and remove duplicated case-conversion implementations

Supersedes #79, #80, #81, #82, #83, #84, #87, #88, #94, #98, #101, #104, #108, #111, #112, and #114.

Validation

• mvn verify
• 661 tests passed
• JaCoCo thresholds met
• Checkstyle, PMD, and SpotBugs clean

[chatgpt-codex-connector]

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