docs: add node infrastructure concept page (Batch 2)

[marc0olo]

Summary

• Creates docs/concepts/node-infrastructure.md with two sections: IC-OS overview (SetupOS, HostOS, GuestOS) and Trusted Execution Environments (SEV-SNP memory encryption, VM launch measurements, attestation reports, sealing keys, upgrade process)
• Updates docs/concepts/https-outcalls.md: replaces the Learn Hub TEE link with the new internal path; removes a stale Learn Hub further-reading link for the skipped HTTPS Outcalls article

Staging files deleted

• .migration/learn-hub/how-does-icp-work/node-infrastructure/overview.md → docs/concepts/node-infrastructure.md
• .migration/learn-hub/how-does-icp-work/node-infrastructure/trusted-execution-environments.md → docs/concepts/node-infrastructure.md#trusted-execution-environments

Sync recommendation

hand-written

[marc0olo]

Review notes

Content and links look good. One soft dependency to note:

Dependency on #209: The "Further reading" section links to protocol/index.md, which only exists once PR #209 merges. Not a hard build failure, but the link will be dead until then. Consider merging after #209 or temporarily removing the link and adding it back post-merge.

No other issues: no banned patterns, frontmatter complete, Learn Hub TEE link correctly replaced with the internal node-infrastructure.md#trusted-execution-environments path, <!-- Upstream: --> comment present.

[marc0olo]

Two items to address before merging:

1. Em-dash on line 89 (banned project-wide)

The "Further reading" bullet uses an em-dash, which is banned per project style rules:

- [Protocol Stack](protocol/index.md) — the replica software that runs inside GuestOS

Fix:

- [Protocol Stack](protocol/index.md): the replica software that runs inside GuestOS

2. Soft dependency on PR #209

The link to protocol/index.md will be a dead link until PR #209 merges and that page exists. Recommend merging this PR after #209 to avoid a temporarily broken link.

[marc0olo]

Feedback addressed:

• Replaced em-dash with colon in node-infrastructure.md line 89 Further reading bullet

Note on the soft dependency: the link to protocol/index.md will still be dead until PR #209 merges. Since #209 is now ready, recommend merging #209 first then this one.