Plan-graph refinement round 1 (owner): chat-font zoom cap + stroke-safe padding

In-chat full plan block:
- TEXT_CAP_SCALE (16.5/12.5): node text renders at text-xs in svg units;
  the block now carries maxWidth = extent × cap + mx-auto, so it still
  fills the column whenever the column is narrower than the cap, but
  never scales node text past the chat prose size (--lh-prose-size).
- GRAPH_PAD (8 svg units) around the full-extent viewBox: centered
  strokes (half outside the geometry) and the −4 glow halo were clipping
  at the frame edges — the padded origin (-8,-8) keeps all ink visible.
  Only the full-extent render pads; the plan window's override viewport
  and the popup's fit margins are untouched.
Test pins updated: mx-auto + max-width:232.32px + viewBox='-8 -8 176 152'.

components/plan-block.tsx

@@ -129,6 +129,17 @@ export function wrapTitle(title: string, maxChars = 20, maxLines = 2): string[]
 	return lines;
 }
 
+// ─── Geometry caps (owner, plan-graph refinement round 1) ─────────────────────
+
+/** SVG-unit padding around the layout extent: strokes are centered on the
+ *  geometry (half bleeds outside the extent) and the glow halo reaches −4 —
+ *  without this pad the outermost node borders clip at the svg edge. */
+export const GRAPH_PAD = 8;
+/** Node titles render at text-xs (12.5px) in svg units. The in-chat block
+ *  scales up to fill the column but NEVER past the chat prose size
+ *  (--lh-prose-size, 16.5px) — the width cap that makes that hold. */
+export const TEXT_CAP_SCALE = 16.5 / 12.5;
+
 // ─── Status styling (the retired panel's color language, unchanged) ──────────
 
 const BOX: Record<PlanNodeStatus, string> = {
@@ -151,6 +162,8 @@ export function PlanDiagram({
 	glowId,
 	markerId,
 	viewBoxOverride,
+	pad: padUnits,
+	textCapScale,
 }: {
 	nodes: readonly LayoutNode[];
 	edges: ReadonlyArray<{ from: string; to: string }>;
@@ -159,12 +172,26 @@ export function PlanDiagram({
 	markerId: string;
 	/** A windowed viewBox (the plan window) instead of the full extent. */
 	viewBoxOverride?: string;
+	/** Pads the viewBox by this many svg units so centered strokes and the
+	 *  glow halo never clip at the extent edges (full-extent renders only). */
+	pad?: number;
+	/** Caps the rendered width at extent × scale — the chat-font-size zoom
+	 *  ceiling for the in-chat block (fills the column, never past prose). */
+	textCapScale?: number;
 }) {
 	const layout = useMemo(() => blockLayout(nodes, edges), [nodes, edges]);
+	// Pad only the full-extent render — the plan window's override viewBox is
+	// a deliberate viewport crop, and the popup keeps its own fit margins.
+	const pad = viewBoxOverride ? 0 : (padUnits ?? 0);
+	const w = Math.max(layout.width, 1);
+	const h = Math.max(layout.height, 1);
+	const vbW = w + 2 * pad;
+	const vbH = h + 2 * pad;
 	return (
 		<svg
-			viewBox={viewBoxOverride ?? `0 0 ${Math.max(layout.width, 1)} ${Math.max(layout.height, 1)}`}
+			viewBox={viewBoxOverride ?? `${-pad} ${-pad} ${vbW} ${vbH}`}
-			className="block h-auto w-full"
+			className={`block h-auto w-full${textCapScale ? " mx-auto" : ""}`}
+			style={textCapScale ? { maxWidth: `${Math.round(vbW * textCapScale * 100) / 100}px` } : undefined}
 			role="img"
 			aria-label="Plan diagram"
 		>
@@ -254,7 +281,17 @@ export function PlanBlock({ data, onOpen }: { data: PlanBlockData; onOpen: () =>
 			title="Open the full plan"
 			className="block w-full text-left"
 		>
-			<PlanDiagram nodes={data.nodes} edges={data.edges} statusOf={statusOf} markerId={markerId} />
+			{/* pad keeps centered strokes + the glow halo inside the frame; the
+		    cap keeps node text at or below chat prose size while still filling
+		    the column when it can (owner, plan-graph refinement round 1). */}
+		<PlanDiagram
+			nodes={data.nodes}
+			edges={data.edges}
+			statusOf={statusOf}
+			markerId={markerId}
+			pad={GRAPH_PAD}
+			textCapScale={TEXT_CAP_SCALE}
+		/>
 		</button>
 	);
 }

tests/render-plan-block.test.tsx

@@ -82,11 +82,14 @@ describe("plan block render", () => {
 		assert.match(html, /data-testid="plan-block-full"/);
 		// Borderless: the wrapper carries no border/rounded chrome.
 		assert.ok(!/data-testid="plan-block-full"[^>]*border/.test(html), "no wrapping chrome");
-		// Fills the column: the svg is w-full with the layout extent as viewBox
+		// Fills the column UP TO the chat-font cap: the svg is w-full +
-		// (leftmost/rightmost nodes hug the edges), height natural.
+		// mx-auto with maxWidth = extent × TEXT_CAP_SCALE, so node text never
-		assert.match(html, /<svg[^>]*class="block h-auto w-full"/);
+		// renders past the 16.5px prose size (owner, plan-graph round 1).
-		// Two stacked nodes: 2*NODE_H + GAP_Y = 136 natural height, width = one node column.
+		assert.match(html, /<svg[^>]*class="block h-auto w-full mx-auto"/);
-		assert.match(html, /viewBox="0 0 160 136"/);
+		assert.match(html, /max-width:232\.32px/); // (160+16) × 1.32
+		// Two stacked nodes: 2*NODE_H + GAP_Y = 136 extent + GRAPH_PAD on
+		// every side (strokes/glow never clip at the edges).
+		assert.match(html, /viewBox="-8 -8 176 152"/);
 		// Snapshot statuses render as carried.
 		assert.match(html, /data-testid="plan-node-a" data-status="visited"/);
 		assert.match(html, /data-testid="plan-node-b" data-status="upcoming"/);