docs(readme): ecosystem cohesion - W3 W6 W8c W8e

- Switch wordmark to canonical .github raw URLs (light + dark via <picture>)
- Audit shields.io badges for brand color #0454F1
- Add Related footer linking siblings in the Upstream-Intelligence ecosystem

Plan: /Users/kevinrichards/.claude/plans/before-we-continue-with-shimmering-minsky.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: byteworthy

README.md

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 <div align="center">
 
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-  <source media="(prefers-color-scheme: dark)" srcset=".github/assets/upstream-wordmark-dark.svg">
-  <img src=".github/assets/upstream-wordmark-light.svg" alt="Upstream" width="220" />
+  <source media="(prefers-color-scheme: dark)"
+          srcset="https://raw.githubusercontent.com/Upstream-Intelligence/.github/main/.github/assets/upstream-wordmark-dark.svg">
+  <img src="https://raw.githubusercontent.com/Upstream-Intelligence/.github/main/.github/assets/upstream-wordmark-light.svg"
+       alt="Upstream" width="220" />
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 # upstream-mcp
@@ -248,13 +250,14 @@ The license on the client code does not grant API service access. Production usa
 
 ## Related
 
-- [upstream.cx](https://upstream.cx) Payer intelligence Platform
-- [upstream-skills](https://github.com/Upstream-Intelligence/upstream-skills) Claude Code skill pack for billing teams
-- [upstream-community](https://github.com/Upstream-Intelligence/upstream-community) Open ML reference implementations
-- [upstream.cx/developers](https://upstream.cx/developers) Full API documentation
-- [Newsletter](https://upstream.cx/newsletter) Monthly network signals digest
+Part of the [Upstream Intelligence ecosystem](https://github.com/Upstream-Intelligence).
 
----
+- **upstream-mcp** — you are here
+- [upstream-skills](https://github.com/Upstream-Intelligence/upstream-skills) — Claude Code skills for billing teams
+- [upstream-community](https://github.com/Upstream-Intelligence/upstream-community) — open ML methodology
+- [awesome-payer-risk](https://github.com/Upstream-Intelligence/awesome-payer-risk) — curated RCM resources
+
+Product: [upstream.cx](https://upstream.cx) · [Newsletter](https://upstream.cx/newsletter) · [Pricing](https://upstream.cx/pricing)
 
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