docs: credit PPT Master source

[Stahl-G]

What changed

• add an English acknowledgement for PPT Master in the main README
• add the matching Simplified Chinese acknowledgement
• link the pinned upstream commit and packaged third-party notice

Why

BriefLoop's initialization panel adapts interaction-layout and visual-system source from PPT Master's MIT-licensed confirm_ui implementation. The public README should thank Hugo He and the PPT Master contributors and make that provenance easy to find.

Validation

• public-safety scan
• terminology check
• version consistency
• release consistency
• git diff check

This is a documentation-only attribution change.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Fix the init-panel notice before linking it

When a reader follows this new attribution link for the initialization panel, the target src/multi_agent_brief/product/init_web/static/THIRD_PARTY_NOTICES.txt still identifies itself as “BriefLoop post-final Review Session assets” and describes derivation through the Quality Panel prototype rather than an init_web-specific notice. Since this README now presents that file as the packaged licensing/provenance record for the initialization panel, downstream users doing attribution or license review are sent to a record that does not match the asset being credited; either update the packaged notice or link to an init_web-correct notice.

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