Left rail: vertically center the claw stack (WorkClaw)

The rail's middle scroll container was a plain block (flex-1 overflow-y-auto
py-4), so the claws clustered at the top with empty space below. Match
WorkClaw: make it a centered flex column —
flex w-full flex-col items-center [justify-content:safe_center] overscroll-contain
[&::-webkit-scrollbar]:hidden — so the stack sits in the vertical middle with
balanced space above/below (safe = no clipping on overflow).

To preserve last commit's left-aligned rows under items-center, the RosterList
ul and the New-claw link are now w-full (else they'd shrink/center). Row gap
0.5→1 to match WorkClaw. (Capture shows no gap on the container itself — the
reviewer's suggested gap-1 there was dropped.)

typecheck/lint(0)/86 unit/30 E2E/6 visual green; workspace-home baseline updated.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

frontend/src/components/shell/LeftRail.tsx

@@ -78,7 +78,9 @@ export function LeftRail({ user, roster, creditsBalance }: LeftRailProps) {
             <X aria-hidden size={16} />
           </button>
         </header>
-        <div className="flex-1 overflow-y-auto py-4">
+        {/* Vertically centers the claw stack in the rail (safe = no clipping
+            when it overflows), scrollbar hidden — matches WorkClaw. */}
+        <div className="flex w-full flex-1 flex-col items-center [justify-content:safe_center] overflow-y-auto overscroll-contain py-4 [&::-webkit-scrollbar]:hidden">
           {roster.length === 0 ? (
             <p className="px-3 text-xs text-muted-foreground">No claws yet</p>
           ) : (
@@ -87,7 +89,7 @@ export function LeftRail({ user, roster, creditsBalance }: LeftRailProps) {
           <Link
             href="/claws/new"
             aria-label="New claw"
-            className="group mt-0.5 flex items-center px-4 py-1 md:group-data-[collapsed=true]/rail:justify-center md:group-data-[collapsed=true]/rail:px-0"
+            className="group mt-0.5 flex w-full items-center px-4 py-1 md:group-data-[collapsed=true]/rail:justify-center md:group-data-[collapsed=true]/rail:px-0"
           >
             <span
               aria-hidden

frontend/src/components/shell/RosterList.tsx

@@ -51,7 +51,7 @@ export function RosterList({ roster }: { roster: Agent[] }) {
   });
 
   return (
-    <ul aria-label="Your claws" className="flex flex-col gap-0.5">
+    <ul aria-label="Your claws" className="flex w-full flex-col gap-1">
       {ordered.map((agent) => (
         <li key={agent.id} className="w-full">
           <AgentRosterItem