Minimal-color round 2 (owner): the chip is label-only — spinner out of the top bar

The round-1 experiment put the braille spinner in the chip's old dot
slot; rejected live: the pill's curve and the square braille cell fought
for space (visually squeezed), and the chat surface already shows
in-flight work (thinking shimmer, the dock) — the chip stating the phase
is its whole job. PhaseChip back to a label-only pill (busy prop
removed, single-child gap dropped); work-state lives in exactly one
place: the sidebar row's spinner. Doc note + test pin the decision so
it doesn't get re-tried blind. Gates: typecheck, lint, 469/469, build.

components/chat.tsx

@@ -605,7 +605,7 @@ export function Chat({
 							Plan
 						</button>
 					)}
-					<PhaseChip phase={phases.at(-1) ?? "probe"} busy={busy} />
+					<PhaseChip phase={phases.at(-1) ?? "probe"} />
 				</header>
 
 				<div className="relative flex min-h-0 flex-1">