docs: document the pygroup element

[bwsw]

Adds documentation for the pygroup pipeline element (#1168), which colocates multiple sequential PyFuncs into a single GStreamer element while preserving a per-stage telemetry span for each colocated function.

• savant_101/70_python.rst: new "Grouping PyFuncs Into a Single Element" section covering syntax, sequential execution, per-stage telemetry, dev-server support, and the sample.
• reference/api/module_config.rst: register PyGroupElement in the PipelineElement inheritance diagram and autosummary.
• getting_started/3_samples.rst: add a catalog entry for the sample.
• samples/pygroup/README.md: add a README for the sample (run steps, stream URLs, and how to inspect the per-stage spans in Jaeger).

Claude-Session: https://claude.ai/code/session_01TbsaV4NhYriTyUqxuzKd8Q

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Note

Low Risk
Documentation-only changes with no runtime, config parsing, or pipeline behavior modifications.

Overview
Documents the pygroup pipeline element for colocating sequential PyFuncs in one GStreamer element while keeping per-stage OpenTelemetry spans.

savant_101/70_python.rst adds Grouping PyFuncs Into a Single Element: YAML with an elements list, why colocation avoids inter-PyFunc queues, guidance on when to use groups vs standalone pyfunc, nested tracing layout, Development Server reload behavior, and a link to the sample. It also fixes the NvDsPyFuncPlugin cross-reference to savant.deepstream.pyfunc.

reference/api/module_config.rst registers PyGroupElement in the PipelineElement inheritance diagram and autosummary.

getting_started/3_samples.rst adds a PyGroup: Colocated PyFuncs catalog entry (features, adapters, sample link).

samples/pygroup/README.md is new: run steps (x86/L4T compose), RTSP/LL-HLS URLs, and how to inspect per-PyFunc spans in Jaeger.

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[Copilot]

Pull request overview

This PR adds end-user documentation for the pygroup pipeline element (introduced in #1168) and documents the accompanying samples/pygroup demo, focusing on syntax, sequential execution semantics, and per-stage OpenTelemetry spans.

Changes:

• Documented pygroup usage and behavior in the Python Function Unit guide, including telemetry span structure and dev-server behavior.
• Registered PyGroupElement in the module configuration API docs (inheritance diagram + autosummary).
• Added the PyGroup sample to the samples catalog and introduced a new sample README with run + telemetry inspection steps.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
samples/pygroup/README.md	New sample README describing how to run the demo and inspect per-stage spans in Jaeger.
docs/source/savant_101/70_python.rst	Adds a new section explaining how to configure and use pygroup, including telemetry details.
docs/source/reference/api/module_config.rst	Updates API docs to include PyGroupElement in hierarchy and autosummary.
docs/source/getting_started/3_samples.rst	Adds a catalog entry for the PyGroup sample.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.