feat(env): add Manager-Based Go2 gait phase terms

[TATP-233]

Summary

• add task-owned NumPy quadruped_gait_phase, preserving the legacy global float32 gait clock and four-foot ordering
• add cached-sensor-view contact and swing-height reward terms with construction-time capability validation
• fail closed on invalid configuration, sensor layout, backward counters, and non-finite runtime data
• keep production Go2 wiring, core manager/backend contracts, runner, IPC, and Hydra configuration unchanged

Scope accounting

• files: 2
• additions: 400
• deletions: 0
• source-derived: 0
• mechanical: 0
• task-owned code: 234
• tests: 166

Validation

• focused tests: 8 passed
• adjacent manager regression: 35 passed
• ruff: passed
• mypy: passed
• pyright: passed
• make test-all: passed (1989 passed, 27 skipped, 276 deselected, 1 xfailed; benchmark module mode 32/33 and script mode 33/34, with one platform-optional MLX skip in each mode)

Refs #1042
Closes #1082

#1042 child policy: all validation above ran locally on the final head. Remote CI/Docs workflows are intentionally not required for child PRs.