refactor: formalize C ABI codec registry via as_c_name/from_c_name #900

Job	Run time
Plugins / Lint (Sherpa-ONNX Plugins)	1m 4s
Plugins / Format Check	20s
Plugins / Lint (NLLB)	2m 9s
UI / Knip (unused code)	14s
Plugins / Lint (Simple Plugins)	43s
Skit / Test (GPU)	1m 45s
UI / Build	12s
Skit / Lint (fmt + clippy)	4m 20s
Plugins / Lint (Whisper)	51s
Skit / Build	10m 32s
UI / Test	31s
E2E / Playwright E2E	15m 48s
Skit / Test	8m 4s
UI / Lint (TypeScript + ESLint)	44s
All Checks Passed	9s
	47m 26s

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