Add 2.8 release notes and NVFlare CLI tutorial

[chesterxgchen]

What this does

Cherry-picks the two recent 2.8 PRs onto main:

• [2.8] Add 2.8.0 release notes [skip ci] #4630: 2.8.0 release notes
• [2.8] Add NVFlare CLI tutorial #4639: NVFlare CLI tutorial replacement and related hello-pt/job stats updates

Verification

• python3 -m pytest tests/unit_test/tool/job/job_stats_test.py tests/unit_test/tool/job/job_abort_test.py tests/unit_test/examples/hello_pt_client_test.py -q: 18 passed
• notebook no outputs/execution counts check
• git diff --check upstream/main..HEAD
• targeted black/isort/flake8
• ./runtest.sh -s

[greptile-apps]

Greptile Summary

This PR cherry-picks two 2.8.0-branch changes onto main: the 2.8.0 release notes and a replacement of the deprecated Job CLI tutorial with a new NVFlare CLI tutorial, along with supporting code updates to the hello-pt example and job_cli.py.

• Documentation: adds flare_280.rst release notes covering CLI expansion, distributed provisioning, Docker/Kubernetes launchers, multi-study support, log streaming, and security hardening; updates welcome.rst, whats_new.rst, previous.rst, and several example docs to reflect the 2.8.0 release.
• hello-pt example: adds --synthetic_data, --train_size, --test_size, and --num_workers flags to client.py and job.py, adds a ValueError guard when the evaluation data loader is empty (matching the custom rule), and adds a corresponding unit test in hello_pt_client_test.py.
• job_cli.py: adds JobNotRunning error handling in cmd_job_stats (previously unhandled), enriches the abort error with a detail field, and adds a matching test case in job_stats_test.py.

Confidence Score: 4/5

Safe to merge — all code changes are additive and well-covered by the 18 passing tests listed in the PR description.

The bulk of the PR is documentation and tutorial replacement, which carry no runtime risk. The three code changes — JobNotRunning handling in cmd_job_stats, synthetic-data support in hello-pt, and the empty-loader ValueError — are each covered by new tests and follow established patterns. One minor concern exists in hello_pt_client_test.py: sys.path.pop(0) could silently remove the wrong sys.path entry if any import during exec_module prepends its own path, potentially polluting the path for later tests.

tests/unit_test/examples/hello_pt_client_test.py — the sys.path.pop(0) cleanup could be made more robust (see inline comment).

Important Files Changed

Filename	Overview
nvflare/tool/job/job_cli.py	Adds JobNotRunning import and proper error handling in cmd_job_stats; also enriches the existing abort error with a detail field. Both changes are consistent with the surrounding error-handling pattern.
examples/hello-world/hello-pt/client.py	Adds synthetic data support, parameterised num_workers/train_size/test_size flags, and a ValueError guard when the evaluation data loader produces zero samples — consistent with the custom rule.
examples/hello-world/hello-pt/job.py	Propagates the new client flags through the recipe's train_args, adds --enable_log_streaming support, and threads all new arguments cleanly into the simulation entry point.
tests/unit_test/examples/hello_pt_client_test.py	New test file verifying that evaluate() raises ValueError on an empty data loader; module loading is correctly isolated, but sys.path.pop(0) is fragile (see inline comment).
tests/unit_test/tool/job/job_stats_test.py	Adds test_stats_job_not_running_exits_1 using the same mocking pattern as existing tests; correctly imports JobNotRunning and asserts exit code, error code, and message content.
examples/tutorials/nvflare_cli.ipynb	New tutorial notebook replacing job_cli.ipynb; covers CLI commands for config, system status, study management, job submit/abort/stats/download, and provisioning — no outputs or execution counts, consistent with CI requirements.
docs/release_notes/flare_280.rst	New 2.8.0 release notes file covering CLI expansion, distributed provisioning, Docker/Kubernetes launchers, multi-study support, log streaming, security hardening, and new examples.
docs/release_notes/previous.rst	Adds flare_272 entry so 2.7.2 is properly listed under previous releases now that 2.8.0 is the current release.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[cmd_job_stats called] --> B{Call session.show_stats}
    B -->|Success| C[output_ok with stats JSON]
    B -->|JobNotFound| D[output_error JOB_NOT_FOUND]
    B -->|JobNotRunning| E[output_error JOB_NOT_RUNNING\ndetail: stats available only while running]
    B -->|AuthenticationError| F[re-raise]
    B -->|NoConnection| G[output_error CONNECTION_FAILED]

    H[cmd_job_abort called] --> I{Call session.abort_job}
    I -->|Success| J[output_ok]
    I -->|JobNotRunning| K[output_error JOB_NOT_RUNNING\ndetail: abort available only while running]
    I -->|AuthenticationError| L[re-raise]

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_{Reviews (1): Last reviewed commit: "[2.8] Add NVFlare CLI tutorial (#4639)" | Re-trigger Greptile}

[greptile-apps]

sys.path.pop(0) assumes example_dir is still at index 0 when the finally block runs. If any import triggered by exec_module prepends its own entry to sys.path, pop(0) silently removes that entry instead of example_dir, leaving the test's path addition permanently in sys.path for subsequent tests. Using sys.path.remove(example_dir) (or a try/except around it) removes the correct entry by value regardless of what happened to the list during execution.

Suggested change

	finally:
	sys.path.pop(0)
	if original_model_module is not None:
	finally:
	try:
	sys.path.remove(example_dir)
	except ValueError:
	pass
	if original_model_module is not None: