docs(agents): restructure AGENTS.md with progressive disclosure and skills.sh integration #1088

Job	Run time
Plugins / Lint (Simple Plugins)	4m 39s
Plugins / Format Check	16s
Plugins / Lint (NLLB)	2m 8s
E2E / Playwright E2E	16m 34s
UI / Build	12s
Plugins / Lint (Whisper)	41s
UI / Lint (TypeScript + ESLint)	39s
Skit / Build	11m 55s
Skit / Lint (fmt + clippy)	4m 3s
Skit / Test (GPU)	1m 54s
Plugins / Lint (Sherpa-ONNX Plugins)	56s
UI / Test	24s
Skit / Test	8m 16s
UI / Knip (unused code)	15s
All Checks Passed	3s
	52m 55s

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