One board, step 4: more than one repository #1293

Part of #1265 — step 4 of 4 (the umbrella's triage comment 6412574627 and Chief's HTML spec 6413937162).

Written-by: Dev4

Scope

One instance today shows one repository. This step makes delivery.repos a list, and every repository gets its own resolved source, its own snapshot and its own block on the board — while a single-repository instance keeps exactly today's DOM.

• delivery.repo (string) stays accepted as a one-element list; delivery.repos is the new shape.
• delivery-repo.js: resolveRepo() becomes per repository — { repo, source } computed per entry, so two repositories cannot share one source line or one NO_REPO_MESSAGE.
• Snapshot cache keyed per repository (the Map<repo, board> Delivery board reads the package repository: an instance shows another repository numbers and says nothing #1250 added), each with its own data-state.
• One repository → no section.bt-del-repo-block; still p.bt-del-repo[data-repo][data-repo-source]. More than one → one section.bt-del-repo-block[data-repo][data-state] + h3.bt-del-repo-head (sticky) per repository.
• Body data-state stays five values; when some repositories read and others do not, the body is partial and the readable repositories still draw.
• Columns are not collapsed here; the visible columns come through one function (stagesOf) so The workflow engine: each node names its Bot and its inputs and outputs, the nodes are drawn as a flowchart, and a node missing an input is refused on the card #1272's repo-dev preset can replace the data source without rewriting the renderer.

Red conditions

1. Two repositories configured → both repositories' cards are on the board, each with its own badge; hard-coding one repository key makes the second repository's cards disappear.
2. One repository → [data-repo-block] count is 0, identical to today; the two layouts are distinguishable by counting.
3. One repository fails to read → body partial, the good repository still draws, the broken one carries its own data-state.
4. No GITHUB_TOKEN → task cards still render and the page says the GitHub side is unavailable, instead of an empty board (Delivery view fails whole when one request fails: a 404 reads as no GitHub connection, with no retry and no per-endpoint diagnosis #1211, using feat(delivery): draw a 7-day line per metric (#1212) #1221's fake-repository fixture).

Owner: Dev4