/* Left-rail navigation chrome — the `rail` ui_layout. * * Markup in app/web/templates/_app_rail.html; activated by * `html[data-ui-layout="rail"]` (stamped by base_ds.html from * instance.ui_layout / AGNES_UI_LAYOUT). Loaded globally but inert * under the default `topnav` layout — every rule is scoped to the * activation attribute, so topnav instances render byte-identically. * * All colors/typography come from `--ds-*` tokens so the rail works * under any palette theme (paper, blue, navy, dark). Widths and * paddings mirror the issue-#896 prototype (240px rail, 9px item * radius, soft active tint). * * Layout: two fixed zones with one scrolling list between them. * [top] New chat * (scroll) the conversations — as many as the free space fits, * scrolling inside it; never truncated, no expand toggle * [bottom] Library · Agents ─ Admin, then the Set up Agnes card, * then the profile in the foot * EVERY row shares one height (`--rail-row-h`) and one treatment, New chat * included — it is an ordinary `.rail-i`, not a control. See the "New chat" * section for the three tinted variants that were tried there and why all of * them are retired. * * COLOUR RULE — the accent marks WHERE YOU ARE, and nothing else: * `--rail-active-bg` → every "you are here" fill (accent tint) * `--rail-hover-bg` → hover, on every hoverable row (neutral wash) * nothing standing → no row carries a resting tint of its own * * The rail has held every version of this rule, so the reasoning matters more * than the values: * * 1. accent on active — broke once New chat took a tint of its own, because * the accent then carried four meanings at once (the button, the active * nav row, the active conversation, the active admin link) and the column * stopped saying which of them you could act on; * 2. accent on New chat, neutral active — cost the accent its use in hover, * since a hovered row and the resting button were the same pale blue; * 3. accent on hover, neutral active — worked, but spent colour on the one * state the user needs no help identifying: the pointer is already there; * 4. accent on active (current), now that New chat is an ordinary row and * nothing competes for it. * * (1) and (4) are the same rule; what makes it viable now is that New chat has * no standing tint. Active is the better owner than hover because it is * PERSISTENT wayfinding — you locate yourself in the column at a glance, * without reading — where hover is transient feedback that only has to be * perceptible. It also lands the accent on New chat for free on /chat, the * landing surface, where New chat IS the active row. * * The invariant to preserve whatever the values: exactly ONE thing in the * column may own the accent. Two owners is what broke every earlier version. */ /* Clearance for the fixed rail — conditional on the rail actually being there. * `data-ui-layout="rail"` is stamped on by base_ds.html from instance * config, but _app_rail.html renders