docs(profile): finish public architecture/documentation gaps

[ClaudiaFang]

Current state

This issue is partially implemented on current main and should no longer be treated as a greenfield documentation task.

Already present:

• organization profile describing public services and the public/private implementation boundary;
• docs/infrastructure-overview.md with a sanitized public infrastructure overview;
• docs/case-studies/heaven-platform.md plus a case-study index;
• profile links to the infrastructure overview, Heaven Platform case study, tools/plugins, and service status;
• a lightweight public service/project catalog in the profile README.

Remaining goal

Close only the gaps that materially improve public understanding without duplicating the profile or exposing privileged topology/configuration.

Remaining audit

• Decide whether a separate implementation/engineering guide is still useful beyond infrastructure-overview.md and the Heaven Platform case study.
• If useful, document reusable engineering principles at a safe abstraction level: IaC, CI/CD, observability, testing, and agent-assisted workflow — without inventories, private network details, credentials, or operational runbooks.
• Audit the profile's public service/project catalog for current links and remove stale entries.
• Verify every public architecture document still respects the public-service / private-implementation boundary.
• Avoid creating a second generic architecture document if the existing overview + case study already communicate the intended model.

Acceptance criteria

• No duplicated architecture pages with overlapping purpose.
• Profile links point to current public documents/services.
• Public docs explain the engineering model without private host/network/inventory/credential details.
• A separate implementation guide is added only if it has a distinct audience/purpose; otherwise this issue may close after the audit.

[ClaudiaFang]

Backlog priority review — 2026-08-04

Priority: P1

Reason: A sanitized public architecture and service catalog converts existing engineering work into reusable documentation, improves project discoverability, and supports Firstsun’s public technical narrative without creating a new runtime product.

Scheduling note: Deliver in bounded sections and require a security review before publication. Absorb overlapping org-profile registration work such as heaven-www#10 into this canonical documentation issue.