GC2D/SelectShine2: reconstruct the unit, match 9 of 13 functions

[rendable]

Fills in the previously empty SelectShine2.cpp and rewrites the header stub.
Nine functions match exactly; four are close but not byte-exact yet.

Function status (GMSP01):

• 100%: ~TSelectShine, startClose, startIncrease, startDecrease,
  TSelectShineManager ctor and dtor, __sinit, TVec2::sub, TVec3::set
• TSelectShine::TSelectShine 99.8%, TSelectShine::move 96.7%,
  TSelectShineManager::initData 96.2%, TSelectShineManager::perform 92.5%
• TSelectShine::makeNewPosition is an empty stub; only its size (0x2c) is
  known from the map.

Header changes:

• Fields named by offset. The old TOptionRumbleUnit* mRumbleOption[8] was
  wrong; it is now TSelectShine* mShines[8]. SelectMenu.cpp is updated at
  its 5 use sites (mShines[...]->mIsSpinning).
• Added TSelectShineManager::getPosition, getAngle and cCenter.

Decisions worth a look. These are guesses to reach the target's codegen, and
none of the names are confirmed against the original source:

• getShinePosition and getShineAngle are fabricated inline wrappers. They add
  one inline layer so JMASSin/JMASCos and TVec3::set / TVec2::sub stay
  out-of-line calls in perform, as in the target. See the new tip in
  docs/AGENT_MATCHING_TIPS.md.
• bezier() in move() is a fabricated inline; each of the four y segments is
  a quadratic Bezier.
• startIncrease and startDecrease declare two unused TVec3 locals to
  reproduce the target's 0x18 extra stack bytes.
• getAngle uses fabsf: fabs on the atan2f result promoted the math to double,
  which the target does not do.
• move() can read y uninitialized when unk28 >= 4.0f, and initData
  dereferences mShines[mCurrent] without a null check. Both follow the target.

Remaining mismatches: register order in move, extra TVec3 copies and larger
stack frames in initData and perform.

docs/AGENT_MATCHING_TIPS.md: adds a section on small functions staying calls
when nested more than three inline levels deep. This is flagged "Needs human
review" as AGENTS.md asks; it may not generalize, and the section can be
dropped without affecting the code.

Checks:

• Full ninja build passes for GMSP01.
• clang-format 21 (same version as CI) is clean on all changed files.
• validate-symbol-order passes for GC2D/SelectShine2.

Note: open PR #189 also edits SelectMenu.cpp and still uses mRumbleOption, so
whichever lands second will need to reconcile the rename.

Generated with Claude Code

[Mrkol]

AI PRs not polished by a programmer are not generally accepted.