fix: add markdown rendering to chat UI and update CUJ2 documentation

[yuanchen8911]

Summary

Add markdown rendering to the Dynamo chat UI so model responses display formatted headings, bold text, lists, and code blocks instead of raw markdown. Also add the Dynamo inference architecture diagram to CUJ2.

Motivation / Context

The chat UI at http://127.0.0.1:9090/chat.html was displaying raw markdown syntax (e.g., ### **Heading**, - **item**) from model responses as plain text, making responses hard to read.

Fixes: N/A
Related: N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• Documentation update

Component(s) Affected

• CLI (cmd/eidos, pkg/cli)
• API server (cmd/eidosd, pkg/api, pkg/server)
• Recipe engine / data (pkg/recipe)
• Bundlers (pkg/bundler, pkg/component/*)
• Collectors / snapshotter (pkg/collector, pkg/snapshotter)
• Validator (pkg/validator)
• Core libraries (pkg/errors, pkg/k8s)
• Docs/examples (docs/, examples/)
• Other: demos/workloads/inference chat UI

Implementation Notes

• Replaced textContent with innerHTML + a self-contained markdown-to-HTML renderer (no CDN dependencies)
• Renderer handles: headings, bold/italic, inline code, code blocks, lists, horizontal rules
• <think>...</think> blocks from reasoning models are still stripped and shown in a styled "thinking" box
• Server now re-reads chat.html on each request for easier development iteration
• Added Dynamo inference architecture diagram (Client → Frontend → NATS → Worker) to CUJ2

Testing

# Tested manually by running chat-server.sh against a live Dynamo deployment
./demos/workloads/inference/chat-server.sh
# Verified markdown renders correctly in browser at http://127.0.0.1:9090/chat.html

Risk Assessment

• Low — Isolated change, well-tested, easy to revert

Rollout notes: N/A

Checklist

• Tests pass locally (make test with -race)
• Linter passes (make lint)
• I did not skip/disable tests to make CI green
• I added/updated tests for new functionality
• I updated docs if user-facing behavior changed
• Changes follow existing patterns in the codebase
• Commits are cryptographically signed (git commit -S) — GPG signing info