[rupayon123]

With ParseTime, decoding "-1s" into a duration field fails with an integer parsing error. The existing duration helper accepts it, but the decode hook only calls that helper for strings starting with a digit.

Try the same helper for negative values too. If it cannot parse one, leave it to the existing decoder so signed integer strings such as "-42" keep working. Environment-expanded duration values follow the same path.

Go 1.26.0 / macOS arm64 validation:

• Ten regression cases fail before the fix; all 16 new cases pass afterward.
• Full coverage and race runs each pass 212 leaf cases, with no skips or failures; statement coverage is 96.7%.
• Vet, build, tidy, formatting and the YAML example pass. Staticcheck retains three baseline diagnostics; Revive reports the same 17 existing warnings.
• Independent checks compare 144 actual decodes with the base: 16 intended improvements, 128 unchanged results, and no regressions. These include signed numeric formats, named types, zero values and overflow.

This preserves the existing duration grammar; it does not add +1s or .5s support. Hosted CI and other Go/OS combinations remain unverified locally.