test: correct root-docs-links' account of what check:links does

[hivecommons-hive]

Test Improvement

Corrects a factually wrong comment in tests/root-docs-links.test.mjs. It is
comment-only: no case, assertion or helper changes, and the file's 7 cases stay
green (npm run test:unit -- tests/root-docs-links.test.mjs: 7 pass, 0 fail).

The file said, at line 10:

and npm run check:links delegates to a Makefile that does not exist.

Measured at main = 7ab301e:

• package.json:10 defines _check:links-md as a loop over root *.md
  calling npx markdown-link-check --config .markdown-link-check.json. There
  is no make invocation anywhere in package.json.
• ls Makefile → no such file, and no source file in the repository mentions
  one.
• .markdown-link-check.json is actively guarded by
  tests/markdown-link-check-config.test.mjs, which derives the honoured key
  set from the installed CLI so a devDependency bump cannot silently disable a
  setting.

So check:links is not vestigial, and a reader of this test was being told it
was. The replacement states the two things that are actually true and that
explain why these offline cases exist: no workflow invokes check:links
(the subject of #1137), and it checks outbound http(s) URLs rather than the
relative on-disk paths these cases resolve — the complementary half, not the
same check.

Related Issue

Refs #1137 (needs-human: #1137's first box adds a scheduled link-check job to
.github/workflows/ci.yml, which this agent's contributor-tier token cannot
push — GitHub rejects any diff touching .github/workflows/** without the
workflows permission. This PR lands only the second box. The exact YAML for
the first is in the issue body.)

Coordination

Touches exactly one file, tests/root-docs-links.test.mjs, which no open PR
modifies: #1090 (scripts/lib/svg-active-content.mjs), #1112 (package.json,
package-lock.json), #1122 (scripts/lib/mdx-active-content.mjs), #1104,
#1110, #1113, #1114, #1117, #1120, #1124, #1126, #1128, #1130, #1133 and #1136
were each checked with gh pr view --json files and none names this path. It
is also disjoint from #1137's workflow half, from the tests/tools/** coverage
cluster (#1128, #1130, #1131) and from the e2e region-attribution cluster
(#1066, #1079, #1097).

---

Filed by quality agent (hold-gated mode). Human review required.

— hive: agent=quality backend=copilot model=claude-opus-5 copilot=1.0.88

[hivecommons-hive]

Important

Held for human review by the hive's ACMM level gate.

This PR was opened by the "quality" agent while Hive policy required a human checkpoint for that agent. Non-outreach agents are held at ACMM L3–L5; the outreach agent is always held because it publishes project-facing communication.

Hive will keep the hold label until a human removes it. Operators can make a deliberate one-off release during an ACMM level change with release_level_holds=true, but level changes never release this hold automatically.