fix: clap CLI definitions and manpage generation

- add #[group(skip)] to all Parser-derived structs
- fix conflicts_with and arg definitions for correct CLI behavior
- refactor bin entry points to support manpage generation

core/man/start-cli/start-cli-util-b3sum.1

@@ -0,0 +1,19 @@
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.TH start-cli-util-b3sum 1  "b3sum " 
+.SH NAME
+start\-cli\-util\-b3sum \- Calculate blake3 hash for a file
+.SH SYNOPSIS
+\fBstart\-cli util b3sum\fR [\fB\-\-no\-mmap\fR] [\fB\-h\fR|\fB\-\-help\fR] <\fIFILE\fR> 
+.SH DESCRIPTION
+Calculate blake3 hash for a file
+.SH OPTIONS
+.TP
+\fB\-\-no\-mmap\fR
+Disable memory\-mapped file I/O
+.TP
+\fB\-h\fR, \fB\-\-help\fR
+Print help
+.TP
+<\fIFILE\fR>
+