Add support for running decimator stage-2 in a separate thread for low power mic configurations.

[shuchitak]

Enabled by defining -DMIC_ARRAY_CONFIG_ENABLE_DECIMATOR_STG2_TASK=1, in addition to -DMIC_ARRAY_CONFIG_LOW_POWER=1

[Copilot]

Pull request overview

Adds an optional low-power configuration that runs the second-stage decimator in a separate parallel task/thread, enabled via -DMIC_ARRAY_CONFIG_ENABLE_DECIMATOR_STG2_TASK=1 alongside -DMIC_ARRAY_CONFIG_LOW_POWER=1.

Changes:

• Extends mic array task startup to optionally spawn an additional “decimator stage-2” task connected via a channel.
• Adds a new decimator_stg2_task() API + implementation and wires it into the low-power decimator path.
• Updates C/C++ task entry points and configuration defaults/docs for the new build-time option.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
lib_mic_array/src/mic_array_task_internal.hpp	Updates internal task entrypoint signatures; adds stage-2 task starter declaration.
lib_mic_array/src/mic_array_task.cpp	Routes low-power decimator startup to 1-stage vs 2-stage-parallel path; adds stage-2 task starter.
lib_mic_array/src/mic_array_task.c	Spawns extra parallel job + channel when stage-2 task is enabled.
lib_mic_array/src/decimator_stg2_task.c	Introduces the stage-2 decimator worker task implementation.
lib_mic_array/api/mic_array/mic_array_conf_default.h	Documents low-power behavior and adds default for MIC_ARRAY_CONFIG_ENABLE_DECIMATOR_STG2_TASK.
lib_mic_array/api/mic_array/decimator_stg2_task.h	New public header for decimator_stg2_task().
lib_mic_array/api/mic_array/cpp/MicArray.hpp	Adds new low-power thread entrypoints and adjusts docs.
lib_mic_array/api/mic_array/cpp/Decimator.hpp	Adds a channel-based parallel two-stage block processing method and c_decimator member.
lib_mic_array/api/mic_array.h	Exposes the new stage-2 task header via the main public include.

Comments suppressed due to low confidence (1)

lib_mic_array/api/mic_array/cpp/MicArray.hpp:174

• The Doxygen comment for ThreadEntry() appears corrupted ("froThsis function m ...") and will render incorrectly in generated docs. Please restore the intended sentence about collecting PDM blocks from PdmRx (which must have already been started) and remove the stray text.

       * This function does not return. It loops indefinitely, collecting blocks
       * of PDM data from @ref PdmRx (which must have already been started),
       * uses @ref Decimator to filter and decimate the sample stream to the

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