Adds bin/gsd-from-source shell wrapper that bun-runs src/loader.ts, so
local commits are live without reinstalling gsd-pi. Patches loader.ts
to respect a pre-set GSD_BIN_PATH (previously it clobbered the env var
with process.argv[1], forcing subagent spawns to point at the .ts
loader path which child_process.spawn can't execute).
Why: working on fixes like #4251 required full `bun install -g --trust
gsd-pi` cycles plus longcat shim re-patching for every iteration.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
