chrome: repo-list partial and fixed-width brand

srht-repo-list renders project listings (repos, databases, spaces) as
the family's event-list cards from a neutral ListItem shape, encoding
the rules the services converged on: h4 title link, visibility as small
muted lowercase text on the right for non-public entries only,
description as a paragraph. The empty state is a parameter.

The brand in srht-nav gains min-width: 15rem so the service switcher
starts at the same x-coordinate on every service — without it the menu
shifts by the width of the red service label when hopping between
services.

chrome: shared page chrome for the instance's custom services

Extract the nav/chrome idiom that compare, spec, dolt and cover each
carried as a private copy (and bench was about to fork as a sixth):
BuildNav over the shared config.ini with the canonical ordering and
paste/pages/hub exclusions, a per-request Page with login/logout/profile
URLs against meta's unified login, embedded srht-nav / srht-env-banner
partials (circle brand + red service label + switcher + login box), and
the generic dict/shortsha template helpers.

Policy decisions the copies had drifted on are baked in: switcher only
for authenticated viewers, hub excluded in the builder rather than the
template, profile link prefers hub's ~username page, environment name
uppercased for the banner. Service-specific needs surfaced by the cover
survey get seams instead of copies: ExtraNav for extra switcher entries,
ContainerClass for full-bleed pages, the config section as an explicit
parameter for the active check.