  TOI-677 b is part of an emerging class of ``tidally-detached'' gas giants
($a/R_\star \gtrsim 11$) that exhibit large orbital eccentricities and yet low
stellar obliquities. Such sources pose a challenge for models of giant planet
formation, which must account for the excitation of high eccentricities without
large changes in the orbital inclination. In this work, we present a new
Rossiter-McLaughlin (RM) measurement for the tidally-detached warm Jupiter
TOI-677 b, obtained using high-precision radial velocity observations from the
PFS/Magellan spectrograph. Combined with previously published observations from
the ESPRESSO/VLT spectrograph, we derive one of the most precisely constrained
sky-projected spin-orbit angle measurements to date for an exoplanet. The
combined fit offers a refined set of self-consistent parameters, including a
low sky-projected stellar obliquity of $\lambda=3.2^{+1.6}_{-1.5}$ deg and a
moderately high eccentricity of $e=0.460^{+0.019}_{-0.018}$, that further
constrains the puzzling architecture of this system. We examine several
potential scenarios that may have produced the current TOI-677 orbital
configuration, ultimately concluding that TOI-677 b most likely had its
eccentricity excited through disk-planet interactions. This system adds to a
growing population of aligned warm Jupiters on eccentric orbits around hot
($T_{\rm eff}>6100$ K) stars.
