refactor: consolidate numpy geometry helpers under unilab.utils

[TATP-233]

Summary

• Move unilab.envs.common.{rotation,math} → unilab.utils.{rotation,math} so the shared numeric helpers live in utils/ alongside device, tensor, nan_guard. Delete the now-empty unilab.envs.common package.
• Fold math.py's lone np_sample_uniform into unilab.utils.geometry so utils/ no longer hosts a single-function module.
• Extract per-env private geometry helpers (previously duplicated across motion_tracking/g1/tracking.py, manipulation/stewart/balance.py, manipulation/allegro_inhand/rotation.py, manipulation/sharpa_inhand/rotation.py, locomotion/go2_arm/base.py, locomotion/go2_arm/manip_loco.py) into a new unilab.utils.geometry module: quaternion normalize, roll/pitch, gravity-z-in-body, orientation-error-local, angular-velocity-from-pair, uniform quaternion sampling, spherical↔cartesian, and a fused frame-transform + 6D-flatten writer.
• Delete dead code: _normalize_quat and _orientation_error_local in go2_arm/base.py no longer have callers after the util replaces them.
• Update all 30+ import sites across src/, tests/, scripts/, sphinx docs, AGENTS.md pointer, and the utils allowlist test.

Numerical equivalence

Each replaced helper was probed against its pre-refactor implementation on random inputs (batched float32 quaternions/positions, various rotation axes, sphere↔cart samples). All 14 checked functions produce bit-identical output:

Function	Bit-equal
np_gravity_z_in_body_from_quat	✅
np_roll_pitch_from_quat (+ stewart float32 wrapper)	✅
normalize_rotation_axis (allegro)	✅
compute_ball_angvel (allegro)	✅
sample_random_quaternion (sharpa)	✅
np_quat_orientation_error_local (go2_arm)	✅
_sphere2cart / _cart2sphere (go2_arm aliases)	✅
np_write_relative_anchor_transform_pos_rot6d (tracking, pos + rot6d)	✅
np_sample_uniform (moved)	✅

normalize_rotation_axis initially drifted by 1 ULP (~6e-08) for non-unit input tuples because np_normalize_axis computes the norm as a Python float (float64). Fixed by pre-casting the input tuple to get_global_dtype() before delegating, so the norm and division happen at the training dtype exactly as before.

Validation

• make test-all → 1410 passed, 27 skipped, 258 deselected (43.15s, coverage 73%).
• Standalone bit-equivalence probes for all 14 refactored functions on random float32 inputs — all bit-identical.
• All env module imports smoke-tested (G1MotionTrackingEnv, StewartBalanceEnv, AllegroRotationPPO, SharpaInhandRotationEnv, Go2ArmBaseEnv, Go2ArmManipLocoEnv, G1BoxTrackingEnv).

Test plan

• make test-all passes
• Bit-equivalence probes on random inputs for every refactored helper
• sample_random_quaternion monkeypatch test in tests/test_sharpa.py still works (import at module scope preserved)
• _cart2sphere direct import in tests/envs/locomotion/go2_arm/test_manip_loco_contract.py still works (aliased at import)
• unilab.utils allowlist test updated with geometry, rotation (and no longer requires math)

[TATP-233]

check

[TATP-233]

关闭本 PR：本次改动已直接合并进 perf/g1-walk-numba-accel 分支（merge commit e7bedcc0），未走单独入 main 的流程。

合并过程中解决了两处冲突：

• tests/utils/test_utils_package_policy.py：白名单取并集，同时保留 geometry、numba_geometry、rotation。
• tests/utils/test_numba_geometry.py：perf 分支在切分之后新增的 unilab.envs.common.rotation 导入改写为 unilab.utils.rotation。

合并后 tests/utils + tests/envs + tests/test_sharpa.py 共 335 用例通过；剩余 4 个 test_g1_motion_tracking_clip_end_* 失败为 perf 分支合并前既存的 _numba_accelerator AttributeError（git stash 已核对），与本次重构无关。