FindExtraFiles now skips hidden files/directories and manifest files
(index.mf, .index.mf) when looking for extra files. Previously it would
report these as 'extra' even though they are intentionally excluded from
manifests by default, making --no-extra-files unusable.
Also includes IsHiddenPath fix for '.' (needed by the new filtering).
path.Clean(".") returns "." which starts with a dot, causing IsHiddenPath
to incorrectly treat the current directory as hidden. Add explicit checks
for "." and "/" before the dot-prefix check.
Fixed in both mfer/scanner.go and internal/scanner/scanner.go.
clawbot