move NeuralAudio implementation to pdnam+; create new MicroNam called pdnam~

[dromer]

• adjust readme
• sort out licensing
• expand MicroNAM example

[Copilot]

Pull request overview

This PR splits PDNAM into two Pure Data externals: a new pdnam~ based on MicroNAM, and a pdnam+~ external that retains the NeuralAudio-based implementation, along with build/packaging updates to ship both.

Changes:

• Replaced the pdnam~ implementation with a MicroNAM-based JSON weight loader and updated its help patch accordingly.
• Added a new pdnam+~ external containing the previous NeuralAudio-based loader and a corresponding help patch.
• Updated build system, submodules, CI runner targets, and README/license notes to reflect the split.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pdnam~.cpp	Switches pdnam~ to MicroNAM + JSON weight parsing and per-sample inference.
pdnam~-help.pd	Updates the help patch to demonstrate the new MicroNAM-based pdnam~ usage.
pdnam+~.cpp	Introduces pdnam+~ using NeuralAudio’s NeuralModel loader/processor.
pdnam+~-help.pd	Adds help patch for the NeuralAudio-based pdnam+~.
data/BossWN-feather.nam	Adds an additional example model for testing.
README.md	Documents the new split (pdnam~ vs pdnam+~) and licensing notes.
Makefile	Reworks build to produce a multi-class library and adds MicroNAM/json include paths.
.gitmodules	Adds MicroNAM and nlohmann/json submodules.
.github/workflows/build.yml	Updates Linux runner targets for CI.

Comments suppressed due to low confidence (2)

.github/workflows/build.yml:48

• runs-on: ubuntu-22.04-arm is not a standard GitHub-hosted runner label (typically ubuntu-22.04-arm64 / ubuntu-24.04-arm64). Also actions/checkout@v6 is not a valid released version. Adjust the runner label and action versions so the arm64 job can start successfully.

    runs-on: ubuntu-22.04-arm
    steps:
    - uses: actions/checkout@v6
      with:
        submodules: recursive

.github/workflows/build.yml:18

• The workflow references actions/checkout@v6, which is not a valid released major version (current major is v4). Update this (and other action references in the file, e.g. upload-artifact) to a valid version so CI doesn't fail before building.

    runs-on: ubuntu-22.04
    steps:
    - uses: actions/checkout@v6
      with:
        submodules: recursive

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