ci(lint): adopt the org reusable lint workflow

[Bryan Fawcett (bryanfawcett)]

Why

The mukoko-dev org ruleset requires five status checks on the default branch
of every repo:

lint / actionlint
lint / JSON validity
lint / prettier
lint / markdownlint
lint / yamllint

This repo has no lint workflow at all, so none of them ever reported. A
required context that never reports is permanently pending — which is why all
six open dependabot PRs sit BLOCKED.

The fix

One job named lint calling nyuchi/.github's reusable-lint.yml. A
reusable-workflow call publishes its checks as <caller job> / <called job>,
and that reusable's jobs are named actionlint, JSON validity, prettier,
markdownlint, yamllint — producing exactly the five required strings.

nyuchi/.github is public, so a reusable workflow in it can be called from any
repo in any org. Verified in production, not assumed: mzizi-dev/agent-tools is
a private repo in a different org and calls the same workflow successfully.
Nothing is duplicated into this org — see mukoko-dev/.github#1.

Content fixes needed to go green

fix	files
3 bare URLs wrapped in <…> (renders identically)	web/MIGRATED.md, web/studio/MIGRATED.md
MD036 scope-disabled around the title block and two closing mottos	ARCHITECTURE.md
MD029 scope-disabled per file	docs/guides/creating-{mini-app,service}.md
prettier reflow	4 × services/*/wrangler.jsonc

On the two scoped disables — both are cases where the rule is wrong about this
content, and each carries a comment saying so:

• ARCHITECTURE.md's **Version 2.0 | February 2026**, _A Product of The Bundu Family_ and _Ndiri nekuti tiri_ are a title block. Promoting them
  to real headings would put taglines in the document's outline.
• The guides put a fenced code block at column 0 after each numbered step, which
  splits the ordered list so markdownlint restarts the count at every step. The
  rendered numbering is correct.

The wrangler configs — checked, not assumed

Prettier reflowed 4 wrangler.jsonc files. I verified before/after are
semantically identical by parsing both (comment- and trailing-comma
tolerant) and comparing the objects — all 4 SAME. The changes are array bodies
collapsing onto one line, plus one dangling trailing comma removed from
_template. No binding, id, bucket name or compatibility flag changed.

.prettierrc gains a *.jsonc override setting trailingComma to "none".
Without it, this repo's "trailingComma": "all" made prettier add trailing
commas to wrangler deploy configs. JSONC tolerates them, but quietly rewriting
deployment config to satisfy a formatter is not a trade worth making. The
override keeps those files under the check without changing their shape.

Verification

All five run locally against this branch and pass: actionlint rc=0, JSON
validity rc=0, yamllint -s rc=0, prettier rc=0, markdownlint-cli2
0 error(s) over 22 files. Proof they can still fail is in the PR
conversation.

Unrelated, but it should not go unsaid

Pushing this branch, GitHub reported 282 Dependabot vulnerabilities on main
(5 critical, 100 high, 151 moderate, 26 low). Far outside this PR's scope, and
raised separately in my report — but that number deserves attention.