feat(managers): port manager core to NumPy

[TATP-233]

Summary

• port the pinned mjlab v1.6.0 manager package into unilab.managers with preserved manager roles, config objects, ordering, and lifecycle semantics
• replace manager-facing Torch tensors, devices, buffers, noise, and RNG with NumPy arrays and an env-owned NumPy generator
• fail closed on invalid shapes, non-finite outputs, unsupported viewer/model mutation, and missing stochastic RNG
• keep the package independent from production NpEnv, backends, Hydra, runners, and IPC

Provenance

Source baseline: mujocolab/mjlab v1.6.0, commit 0fb8a681136be94ffc636a3dd423cabb97d91f10, Apache-2.0. Every source-derived file records the upstream path and modification notice.

Change accounting

• source-derived surface: 18 manager/buffer/noise files, 3,632 lines
• mechanical NumPy adaptation and upstream-derived tests: included in those source files plus 722 test lines
• UniLab-specific glue: 52 lines in the private typed context module
• modified existing: pyproject.toml and uv.lock, +15 lines for PrettyTable
• deleted existing UniLab code: none; upstream Torch device, viewer GUI, and direct model-mutation paths were intentionally omitted
• total: 26 files, 4,421 added lines; within the source-aligned exception

Validation

• focused manager suite: 30 passed
• ruff: passed
• mypy: passed
• pyright: passed
• make test-all: 1,799 passed, 24 skipped, 1 xfailed; benchmark import smoke passed 65/67 with two platform-optional mlx skips

Implements #1045
Umbrella: #1042