docs: refine front-door README QA

Update section 03 front-door label to the market-specific wording after live README QA.

Author: Zer0pa-Architect-Prime

README.md

@@ -65,7 +65,7 @@ python -m pytest -q tests/test_music_authority_roundtrip.py tests/test_music_exp
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-<div><b>03 · VALUE</b></div>
+<div><b>03 · VALUE OF MARKET</b></div>
       <div>$10.8<span>B</span></div>
       <div>Music publishing grows; the symbolic-score archive sits <b>unpriced inside publisher and rights workflows.</b></div>
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