Even with info/ok/warn fixed to stderr, raw command output
from git clone and cargo build was still leaking to stdout
through 2>&1 | tail -5.
Fix: added >&2 after tail -5 so ALL intermediate command output
goes to stderr, leaving only the final echo on stdout.
Same fix as gyandoot-release: ensure_gyandoot_binary() detects
whether we're in source repo, binary repo, or need to clone.
install_binary() now takes a path parameter.
The old banner was a handwritten ASCII art that didn't actually
spell 'GYANDOOT'. Replaced with proper figlet 'standard' font
output so the banner is readable and correct.
