Preserve whitespace in literal-only number format sections

[developer0hye]

Summary

• preserve leading and trailing whitespace decoded from literal-only number-format sections
• keep escaped spaces in zero-display formats so right-aligned output retains Excel spacing
• extend the Fix literal-only zero number format sections #361 regression to assert the complete formatted string

Problem

#361 correctly selects and decodes a placeholder-free zero section, but the early return trims its result. For #,##0_);[Red]\(#,##0\);\-\ \ that changes the requested - display to -, shifting a right-aligned dash by the width of two spaces.

Testing

• cargo test --lib (119 passed)
• cargo clippy -- -D warnings
• cargo +nightly fmt --all -- --check
• git diff --check

Follow-up to #361.

[developer0hye]

CI is currently red for failures already present on the base branch, rather than for this two-line change:

• build (1.88.0) resolves aes 0.9.3, which requires Rust 1.89. The repository does not pin a lockfile for this job.
• formatting reports existing rustfmt drift across unrelated files such as src/helper/date.rs, src/reader/driver.rs, and src/writer/streaming_writer.rs.

The same base-wide failures are visible on the recently merged #361 and on the upstream master workflow. Locally, the focused regression is red before the change and green after it; cargo test --lib passes all 119 tests, and cargo clippy -- -D warnings passes.

[MathNya]

Thank you for the PR.
I'll go ahead and merge it.