documentation: link docs/ci-required-checks.md from the docs map

[codeforester]

Goal

Make docs/ci-required-checks.md discoverable from the repo's normal
documentation entry points.

Background

Found during a pre-release documentation sweep (2026-09-21), reviewed against
origin/main (40ba3e3, "docs(release): prepare v0.2.0 rehearsal and owner
handoff (#317)"). docs/ci-required-checks.md documents the default-branch
protection ruleset (Base default branch protection, ruleset 17625058) and
its required GitHub Actions status-check contexts (base/issue-branch-policy,
validate, validate-ubuntu, validate-base-cli-source, and more). It is a
real, substantive operational runbook, but it is not linked from README.md,
CONTRIBUTING.md, docs/README.md (if present), or any other tracked
markdown file — it's only discoverable by browsing docs/ directly.

This is the same pattern found in basefoundry/base-cli-demo's
docs/branch-protection.md during the same sweep: a required-checks runbook
that exists but isn't linked from any entry point.

Scope

• Add a link to docs/ci-required-checks.md from the repository's
  documentation entry point(s) — README.md and/or CONTRIBUTING.md,
  wherever repository maintenance/ops docs are otherwise pointed to.
• No content change to docs/ci-required-checks.md itself is required unless
  the linking pass surfaces something stale (e.g. a ruleset ID or check
  context that no longer matches the live branch-protection configuration —
  worth a quick cross-check while touching this).

Acceptance Criteria

• docs/ci-required-checks.md is linked from at least one tracked
  markdown entry point.
• The required-check contexts and ruleset ID it documents are confirmed
  current (or corrected) against the live main branch protection
  settings.
• git diff --check passes.

Validation

git diff --check

Non-Goals

• Not changing the branch-protection ruleset or its required checks.

Project Fields

• Status: Backlog
• Priority: P3
• Size: T
• Area: Docs
• Initiative: Adoption Polish
• Milestone: v0.3.0

Agent Assignment

Assignee: @codeforester. The issue scope and acceptance criteria define the implementation boundary.