docs: add Aging Sidekick hosted pilot blueprint

[bradtaylorsf]

Summary

Add an Aging Sidekick hosted pilot blueprint that shows the intended end-to-end workflow for an Astro and Sanity marketing site using Slack or website submissions, GitHub issues, Alpha Loop automation, PR previews, QA handoff, feedback, and resume.

Why this matters

A concrete reference implementation will make the hosted workflow easier to validate and easier for other website/app teams to copy. Aging Sidekick is intentionally modest in scope: content, copy, visual polish, generated imagery, SEO, and small Astro/Sanity changes are good early automation targets, while production deploys and risky schema/auth work stay human-gated.

Proposed approach

• Add a docs/example blueprint for Aging Sidekick or a genericized examples/hosted-marketing-site recipe.
• Define the target workflow: Slack or website request -> GitHub issue -> triage -> policy check -> implementation -> PR/preview -> QA notification -> human feedback -> resume or follow-up issue.
• Provide recommended labels, issue templates, automation policy, event destinations, and feedback ingestion adapter shape.
• Define safe initial automation scope and human-gated scope.
• Include example QA handoff payloads and example feedback comments.
• Capture what needs to be configured in the downstream repo versus what belongs in Alpha Loop core.

Acceptance criteria

• Blueprint documents the complete Aging Sidekick-style request-to-PR-to-feedback workflow.
• Blueprint includes recommended labels and issue templates for co-founder website requests.
• Blueprint includes a safe automation policy for an Astro/Sanity marketing site.
• Blueprint includes event destination examples for Slack and a custom web service.
• Blueprint includes feedback ingestion examples that create GitHub comments and trigger resume --issue.
• Blueprint defines safe automation scope: copy, content, generated images, SEO, visual fixes, and minor Astro changes.
• Blueprint defines human-gated scope: Sanity schema changes, auth, analytics, dependency upgrades, secrets, production deploys, and major redesigns.
• The docs clearly distinguish reusable Alpha Loop capabilities from Aging Sidekick-specific setup.

Out of scope

• Changing the Aging Sidekick repo directly from this issue.
• Building a production Slack app.
• Production deployment automation.

Related

• Parent epic: Epic: Hosted Alpha Loop for 24/7 repo stewardship with human feedback loops #293
• Serves as the first reference/pilot for hosted Alpha Loop on a real marketing site.

[bradtaylorsf]

Part of #293