fix(capy-install): the launch file appends the checkout's bin/ to PATH (GSTA-167)

A /ship child that sourced only the launch file got 'gstack-ship-budget: command
not found' (exit 127). The file now appends <checkout>/bin once, after everything
already on PATH, so it shadows nothing.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/capy-install.md

@@ -423,6 +423,9 @@ GSTACK_LAUNCH_FILE: <verdict file without .json>.env
 
 `GSTACK_LAUNCH_FILE` names the same assignments as a sourceable script (mode
 0600, beside the verdict under the state root; the PATH prepend is idempotent).
+The file also appends the checkout's `bin/` directory to PATH, after everything
+already there and only once, so a shell that sourced only this file runs a bare
+`gstack-ship-budget` (GSTA-167: a /ship child got `command not found`, exit 127).
 The file is part of the ok verdict: a passing run that cannot write it exits 1
 with `gstack: fail launch-file — could not write the launch file <path>; fix:
 make <dir> writable, or set GSTACK_STATE_ROOT to a writable directory