docs: working remote-gdb workflow (sysroot-empty, single-client, SIGINT-to-break)

Solved the gdbserver workflow: the freeze was remote symbol reads (fix: sysroot +
debug-file-directory to an empty dir) and the protocol 'timeout' errors were an IDA
co-connection (gdbserver is single-client). catch-load was unreliable; SIGINT the gdb
process to break into the booted server, then bases via info proc mappings + break by
base+RVA. Verified EncodeField @ ns+0x4334d0 (prologue 55 48 89 e5 41 57 41 56). Encoders
only fire for real network clients (bots have no netchan).