Add HealDAv2 video data assimilation model wrapper

[negin513]

Description

Adds HealDAv2, the earth2studio wrapper for the HealDA-v2 video data assimilation model (physicsnemo.experimental.models.healda.VideoHealDA, dit-5B). The model jointly produces an 8-frame / 48-hour window of global analyses at 6-hour spacing on the HEALPix level-6 grid; the final frame (lead_time == 0) is the present-time analysis.

Key differences from the v1 HealDA wrapper:

• Pressure-level conventional obs normalization (conv-plevel): vertically structured conv channels are binned to the nearest of 13 ERA5 pressure levels and z-scored with per-level statistics, using the expanded 92-channel vocabulary — matching the current healda training configuration
• Infrared hyperspectral sounders (IASI, CrIS-FSR, AIRS): footprints are pivoted and PCA-encoded to 32 latent observations each via bundled PCACodec artifacts
• 50-dim unified observation metadata (features v2) as a pure-torch port (no Triton dependency)
• Output carries a lead_time dimension covering the full 8-frame window

New files:

• earth2studio/models/da/healda_v2.py — the wrapper
• earth2studio/models/da/healda_v2_utils.py — self-contained ports of the sensor vocabulary, conv-plevel expansion, PCA codec, and metadata featurization (no dependency on the internal healda package)
• test/models/da/test_da_healda_v2.py — 23 unit tests incl. hand-computed normalization/channel-mapping checks

Draft status / remaining work

• Checkpoint: awaiting the pressure-level-normalization training checkpoint and its DCP → physicsnemo .mdlus conversion; load_default_package is stubbed until the HF package is published
• nvidia-physicsnemo pin bump in the da-healda extra (released <=2.1.1 predates VideoHealDA)
• docs/modules/models_da.rst entry + example script
• Package-marked integration test
• Dataset registration: NNJA (NOAA-NASA Joint Archive, CC BY 4.0, s3://noaa-reanalyses-pds) Nspect + DGPTT registration in progress; ERA5/UFS Replay coverage under the HealDA v1 submission being confirmed

Preprocessing/API review is welcome now — the above only affect release, not the code shape.

Checklist

• Unit tests pass (mocked model, CPU)
• v1 HealDA tests unaffected
• black / ruff / mypy clean

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