An edge that is not drawn, and a panel that stopped eating the site

`hx-get=""` is not "fetch nothing". htmx looks for the attribute, not for a
value, so the empty one the canvas rendered before a chat existed was a real
request for the empty path -- which the browser resolves against the current
document. Opening the canvas on the new-chat screen fetched the new-chat screen
and swapped the whole site into the panel. The attribute is omitted now, and a
test refuses an empty verb anywhere on the page.

Which panels can exist is the server's answer; which are offered is the
browser's. Both need an agent chat on a chosen connection, and before a chat
exists those are controls in the composer -- so answering with the first profile
offered a terminal on an ordinary chat with nothing selected. They follow
`lembas:agent-target` now, and an open panel whose target goes away is closed
rather than left showing one machine under another's name.

`.tabs__body` is only sometimes the scroller: true where the tabs are a bounded
flex child, false under the admin layout, where the page scrolls instead. So
setting its scrollTop on every tab change had never once run on /admin/prompts,
silently, while the reader was dragged to the bottom of a document that had just
got shorter. The rule names the position now, and the handler finds the
container that actually scrolls.

The two top borders come off. They were what made the misalignment at the bottom
of the shell visible; `--footer-height` stays, because two ends at different
heights are visible without a line to prove it. The top of the shell keeps its
line -- there, everything is `--header-height` and aligns by construction.

And one version. pyproject carried its own copy and had drifted three minors
from the one everything actually reads.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/web/static/css/admin.css

@@ -1,8 +1,22 @@
 /* Settings and administration screens. */
 
-/* --- Page scaffolding ------------------------------------------------------ */
+/* --- Page scaffolding ------------------------------------------------------
+   One scroll container per screen, and this is the rule that decides which.
+
+   `.admin-scroll` is it on every admin page. `.tabs__body` is it only where the
+   tabs are a *bounded* flex child -- `.main > .tabs` on the settings page --
+   which is why the selector below says so rather than naming the class alone.
+
+   It used to name the class alone, and the result was two scrollers stacked on
+   /admin/prompts, where `.tabs` sits inside `.admin-scroll > .admin-page`, a
+   plain block. `flex: 1` and `min-height: 0` mean nothing there, so
+   `.tabs__body` had `height: auto` and never scrolled while still declaring
+   `overflow-y: auto` -- and everything written to reset "the scroller" reset
+   that one, silently, while the reader was lost in the other. Under
+   `.admin-scroll` the body is now an ordinary block and the page scrolls as one.
+*/
 .admin-scroll,
-.tabs__body {
+.main > .tabs > .tabs__body {
   flex: 1;
   min-height: 0;
   overflow-y: auto;