Centralize CLI argument parsing and reject surplus positionals

[Widthdom]

Closes #213

What changed

• Parse options, option values, and positional arguments in one CliParser.Parse() pass.
• Store OldFolder, NewFolder, and optional ReportLabel in the structured CliOptions result.
• Replace the 35-field positional CliOptions constructor with named properties and defaults.
• Reject a fourth positional argument with usage information and exit code 2.
• Preserve two- and three-positional invocations, supported option placement, automatic report labels, wizard execution, and --creator behavior.
• Update the English/Japanese user guide and changelog.

Root cause

Flag parsing, option-value skipping, positional extraction, validation, and consumption were split between CliParser, RunPreflightValidator, and ProgramRunner. The second positional scan collected every non-option token while ProgramRunner consumed only the first three, so surplus positional arguments disappeared silently. The positional CliOptions constructor also made option additions order-dependent.

User impact

Valid commands continue to work, including:

nildiff oldfolder newfolder --creator
nildiff oldfolder newfolder reportlabel --creator --no-il-cache --coffee

A fourth positional argument now produces usage information and exits with code 2 instead of being ignored.

Validation

• dotnet build FolderDiffIL4DotNet.sln --nologo — passed with 0 warnings and 0 errors.
• Focused CLI/parser/validator/wizard/override tests — 120 passed, 0 failed.
• Release suite — 2019 passed and 1 real-disassembler E2E test skipped; 3 Git-fixture tests initially failed because the local global Git config required an SSH signing-key passphrase.
• Those 3 Git-fixture tests were rerun from the Release test assembly with commit.gpgsign=false — 3 passed, 0 failed.
• git diff --check — passed.
• Final cdidx status --check --json — fresh and complete, with 0 failed checks.