[ENG-3771] projects-cli-0: explicit projects CLI

[mrmoxon]

Summary

• add the prime project command group plus Projects API/context helpers
• support explicit project attachment for training runs, eval pushes, hosted evals, and artifact assignment/removal
• keep train/eval behavior explicit-only: no active-project defaulting in this tranche

Validation

• uv run pytest packages/prime/tests/test_rl_config.py packages/prime/tests/test_projects_cli.py packages/prime/tests/test_eval_push.py packages/prime/tests/test_hosted_eval.py packages/prime/tests/test_rl_api.py packages/prime/tests/test_deployments.py packages/prime-evals/tests/test_evals.py -q
• uv run ruff check packages/prime/src/prime_cli/commands/rl.py packages/prime/src/prime_cli/api/projects.py packages/prime/src/prime_cli/commands/projects.py packages/prime/src/prime_cli/utils/projects.py packages/prime/src/prime_cli/commands/evals.py packages/prime/src/prime_cli/utils/eval_push.py packages/prime/src/prime_cli/verifiers_bridge.py packages/prime/tests/test_projects_cli.py packages/prime/tests/test_eval_push.py packages/prime/tests/test_hosted_eval.py packages/prime-evals/src/prime_evals/evals.py packages/prime-evals/tests/test_evals.py

Stacked with #732, which contains the default-project UX layer.

---

Note

Medium Risk
Touches many Lab CLI paths and remote APIs (projects, RFT runs/adapters, evaluations); the environments hub lookup endpoint change could affect eval pushes if the backend contract differs.

Overview
Introduces Lab projects end-to-end: a new prime project command group (create/list/show/use/current/update/clear, plus assign/remove for runs, evals, and adapters), a Projects API client, and workspace active-project context (.prime/lab/context.json, optional PRIME_PROJECT_ID) with team-scope checks.

prime lab setup can create or bind a default project (--project, --project-name, --no-project). prime train and prime eval gain --project / --no-project and send project_id when creating or updating hosted training runs, eval pushes, hosted evals, and post-run hub uploads. RL and deployments clients add PATCH helpers for run/adapter project membership; prime-evals adds project_id on create, assign/clear on update, and switches owner environment lookup to POST /environmentshub/lookup.

READMEs document project workflows and artifact attachment. Tests cover CLI, lab setup project behavior, eval/train forwarding, and API payload shapes.

^{Reviewed by Cursor Bugbot for commit e911d54. Bugbot is set up for automated code reviews on this repo. Configure here.}