Resolve relative item links and name the phase progress bar

[Lenoux01]

Why

Two behaviours the first <Roadmap> consumers (new-campus#142, hn-monorepo#1529) had built into their local renderers and lost when they switched to @hansenexus/nextup/react@0.1.3. Both belong in the package so every site gets them.

Closes #3

What

Progress bar gets an accessible name — ui-react/index.tsx, render-html.ts (the web component and build --site share this markup; the site template has no bar of its own).

Before: role="progressbar" aria-valuenow="<pct>" aria-valuemin="0" aria-valuemax="100", no name — a screen reader announced a bare bar.
After: role="progressbar" aria-label="3 of 8 done" aria-valuemin="0" aria-valuemax="8" aria-valuenow="3". The label is the existing localized Strings.progress ("3 of 8 done" / "3 von 8 erledigt"), counted in items, not percent. Markup and .nextup-* classes are otherwise identical.

Relative item links leave resolved — new links.ts, applied in project.ts (toPublic and toInternal, so build, serve, mcp and both renderers all see the same hrefs), warned about in validate.ts (V15).

url in roadmap.yaml	in the projection
docs/x.md, ./docs/x.md, /docs/x.md, docs/x.md#sec	https://github.com/<meta.repo>/blob/HEAD/docs/x.md (fragment/query kept)
https://…, //cdn.…, mailto:…, tel:…	untouched
#section	untouched
../outside, ?query-only, or any relative link with no repo known	dropped; validate warns V15 naming item + link

HEAD rather than a fetched default branch: GitHub resolves it server-side, so the output is byte-identical with and without a token and build --check never reports drift because master became main. meta.repo is required by the schema, so the "no repo" branch is only reachable through the resolveLink(url, repo | null) API; V15 fires on links that cannot map (escape the repo root, query-only).

Docs: README (yaml example + rule paragraph), roadmap-yaml.md (new ### links section; links was mislabelled "internal"), validation.md (V15 row), sites.md, CLAUDE.md ("Item links leave resolved").

Version bumped to 0.1.4. No tag, no publish. bun run schema:gen output unchanged.

How verified

bun run lint       Checked 54 files in 19ms. No fixes applied.
bun run typecheck  (three tsconfigs, clean)
bun run test       Test Files  15 passed (15)   Tests  150 passed (150)   (was 14 / 136)

New tests: links.test.ts (one case per rule above), project.test.ts (public + internal ship the resolved examples/dev-empire link docs/PLAN.md#phasing → …/blob/HEAD/docs/PLAN.md#phasing; mixed list keeps absolute/mailto/fragment and drops ../), validate.test.ts (V15 path + message), ui-react/index.test.tsx and view-model.test.ts (exact progressbar attribute string in en and de; never aria-valuemax="100"), wc/index.test.ts (attributes read back from the shadow root, label follows lang).

CLI smoke on a scratch roadmap with docs/design/blueprint-module.md and ../elsewhere.md:

$ nextup validate
roadmap.yaml: warning V15 items[0].links[1].url: "a" link "out" (../elsewhere.md) cannot be resolved against acme/smoke and is dropped from the projections — use a repo-relative path, an absolute URL, mailto: or #fragment
ok roadmap.yaml (1 items, 1 phases, 1 warning(s))          exit 0
$ nextup build --audience public --no-github
"url": "https://github.com/acme/smoke/blob/HEAD/docs/design/blueprint-module.md"   (the ../ link is gone)

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