Roman Numeral Place-Value Inspector

Goal Build a tiny offline tool that converts one integer into its canonical Roman numeral and reveals how each decimal place contributes to the result. Deliverable Submit one self-contained HTML file with a descriptive .html filename, no larger than 24 KB. It must work locally without a server or internet connection. Requirements 1. Provide one labelled numeric input starting at 2026 and accepting integers from 1 through 3999. 2. Update immediately to show the canonical uppercase Roman numeral using standard subtractive pairs IV, IX, XL, XC, CD, and CM. 3. Show a compact four-row decomposition for thousands, hundreds, tens, and ones, including the decimal digit and its Roman token; use a clear placeholder when a token is empty. 4. Include visible reference checks for 4 = IV, 9 = IX, 944 = CMXLIV, and 2026 = MMXXVI. 5. For blank, fractional, nonnumeric, or out-of-range input, show a specific inline message and remove any stale numeral or decomposition. 6. Use keyboard-operable native controls, visible focus, a live result announcement, strong contrast, and a layout usable from 360 to 1200 CSS pixels. Negative scope No reverse Roman-to-decimal mode, overline notation, zero or negative-number notation, clocks, dates, quizzes, random values, external assets, libraries, network requests, storage, clipboard access, tracking, accounts, or extra files. Pass/fail acceptance gates - One self-contained HTML file, 24 KB or smaller, that works offline without external resources. - Exact results for the four visible checks plus 1 = I and 3999 = MMMCMXCIX. - Immediate valid and invalid behavior, one input, and the four-place decomposition are present. - Required accessibility signals are present and there is no prohibited code or feature. Scoring rubric (100 points, in order) 1. Conversion and boundary correctness: 50 points. 2. Decomposition clarity and scope compliance: 25 points. 3. Accessibility and error handling: 15 points. 4. Visual polish and readable code: 10 points. Tie-breaker Prefer the submission whose conversion logic and boundary behavior are easiest to verify from readable code; then prefer the clearest decomposition. Visual styling is creatively open.