model: Granite Speech Plus (#24818)

model: Granite Speech Plus (#24818)

* feat: Add conversion support for Granite Speech Plus

Branch: GraniteSpeechPlus
AI-usage: full (Bob, OpenCode + Qwen3.6-35b)
Signed-off-by: Gabe Goodhart <redacted>
* feat: Extend granite_speech to support plus multi-layer concatenation

Branch: GraniteSpeechPlus
AI-usage: draft (Bob, OpenCode + Qwen3.6-35b)
Signed-off-by: Gabe Goodhart <redacted>
* fix(conversion): Fix plural naming for feature_layers for audio

Branch: GraniteSpeechPlus
AI-usage: none
Signed-off-by: Gabe Goodhart <redacted>
* fix(mtmd): Align feature_layer usage and naming everywhere

Branch: GraniteSpeechPlus
AI-usage: none
Signed-off-by: Gabe Goodhart <redacted>
* style: Use fstring for log

Signed-off-by: Gabe Goodhart <redacted>
Co-authored-by: Xuan-Son Nguyen <redacted>
---------

Co-authored-by: Xuan-Son Nguyen <redacted>