feat(runtime): RuntimeData on RuntimeConfig for platform data files

[andrew-vogulkin]

Summary

Adds RuntimeData to RuntimeConfig so a task can declare platform data files, by data-file id, that the hosted rollout box provides to the environment under a mount path. This is the SDK half of the rollout data layer; the control plane resolves ids to storage and the EC2 daemon mounts them (monorepo change follows).

• RuntimeDataFile(file_id, path) and RuntimeData(files, mount_path, mode) in hud/eval/runtime/core.py; RuntimeConfig.data, omitted from JSON when unset, replaced whole by with_overrides.
• Exported from hud.eval.runtime, hud.eval and hud.
• Docs: "Data files" section in docs/v6/reference/runtime.mdx.
• Tests: hud/eval/tests/test_runtime_data.py (defaults, serialization, malformed payloads, override semantics); export test updated.

The block is declarative: which files and where they appear. No bucket or prefix is ever named by a task. Files are bound into the container writable (overlay, the default, copy-on-write to local disk) or read-only (readonly). HUD-hosted EC2 rollouts only; other runtimes reject data.

Test plan

• pytest hud/eval/tests/test_runtime_data.py hud/tests/test_init_module.py hud/tests/test_init.py (12 passed)
• ruff check and format on touched files
• Control-plane contract test in the monorepo passes against this model (backend and SDK serialize the block identically)
• End-to-end in dev-andrei: two tasks declaring one CSV each read it from /data; each container saw exactly its own file

🤖 Generated with Claude Code

---

Note

Low Risk
Additive, optional RuntimeConfig schema and exports with pydantic validation; mounting and enforcement live in the platform, not in SDK runtime providers in this PR.

Overview
Adds RuntimeData / RuntimeDataFile and an optional RuntimeConfig.data block so tasks can declare HUD Data files by id and where they appear in the environment (default mount /data, overlay or readonly mode). The SDK serializes the block like other nested runtime options (omitted when unset) and with_overrides replaces the whole data block rather than merging file lists.

RuntimeData and RuntimeDataFile are exported from hud, hud.eval, and hud.eval.runtime. Reference docs gain a Data files section describing EC2 hosted-rollout behavior, contrast with DataFileArg, and unsupported local/cloud runtimes. New tests cover defaults, JSON shape, validation failures, and override semantics.

^{Reviewed by Cursor Bugbot for commit 93dffa6. Bugbot is set up for automated code reviews on this repo. Configure here.}