infra: cross-reference audit for new concept pages (PRs #209-217)

[marc0olo]

Background

PRs #209-#217 add ~20 new concept and reference pages as part of the Learn Hub migration. Each PR focused on consuming its own staging files and updating the inbound links it was already aware of. A systematic check of whether existing docs pages should now link to the new pages was out of scope for individual PRs.

Task

After all PRs #209-#217 merge, do a cross-reference audit to wire up missing inbound links from existing content to the new pages.

Pages to audit inbound links for

New page	Likely missing inbound links from
concepts/protocol/ (index + 6 sub-pages)	Guides that describe consensus, message routing, execution, or state sync in passing -- none currently link into this directory
concepts/node-infrastructure.md	Security guide, any guide mentioning TEEs or node hardware
concepts/edge-infrastructure.md	Frontend guides, asset canister guide
concepts/evolution-scaling.md	Network overview, governance/NNS concepts
concepts/certified-data.md	network-overview.md (two references to certified-variables.md that could also link to the concept page)
concepts/principals.md	Authentication guides, canister-calls guides, any guide that mentions principals without linking
concepts/chain-fusion/ sub-pages	Chain fusion guide pages link to the top-level index but not yet to individual deep-dive concept pages
concepts/sns-framework.md	SNS launch guide, governance concept page
references/nns-proposal-types.md	NNS governance guides
references/sns-dao-settings.md	SNS managing guide
concepts/tokenomics.md	Governance concept, cycles concept, getting-started content
concepts/token-ledgers.md	ICRC/ledger guides, DeFi guides

Approach

For each new page above:

1. grep -r "topic keyword" docs/ --include="*.md" --include="*.mdx" -l to find pages that discuss the topic
2. Check whether those pages already link to the new concept page
3. Add a link where missing and contextually appropriate

Acceptance criteria

• Every major new concept page has at least one inbound link from a related guide or getting-started page
• No existing guide mentions a topic without linking to its dedicated concept page when one now exists
• npm run build passes after changes