fix(chat): flatten tool detail indentation

apps/desktop/src/styles/messages.css

@@ -2727,6 +2727,12 @@
   color: var(--ds-text-secondary);
 }
 
+/* Tool details stay in the tool row's level rather than adding a second inset. */
+.tool-row:not(.thinking):not(.subagent-topology-node) > .tool-row-body {
+  margin-left: 0;
+  padding-left: 0;
+}
+
 .disclosure-collapse-rail {
   position: absolute;
   inset-block: 0;

apps/desktop/test/transcript-style.test.mjs

@@ -104,6 +104,18 @@ test("tool block bodies stay bounded and role-coded", () => {
   assert.doesNotMatch(permissionArgs, /white-space|font-family/);
 });
 
+test("tool details do not add a second visual indent", () => {
+  const toolDetailStyles = stylesSource.match(
+    /\.tool-row:not\(\.thinking\):not\(\.subagent-topology-node\) > \.tool-row-body \{([^}]*)\}/
+  )?.[1];
+  assert.ok(toolDetailStyles);
+  assert.match(toolDetailStyles, /margin-left:\s*0;/);
+  assert.match(toolDetailStyles, /padding-left:\s*0;/);
+  // Thinking and topology have separate visual hierarchies and keep their
+  // dedicated layout rules rather than inheriting the flat tool detail rule.
+  assert.match(stylesSource, /\.subagent-topology-node > \.tool-row-body,[\s\S]*?margin-left:\s*38px;/);
+});
+
 test("assistant turns stay transparent full-width prose", () => {
   assert.match(
     stylesSource,

docs/spec/04-ux/08-component-spec.md

@@ -1948,7 +1948,10 @@ twice.
 
 - Outer row: transparent, borderless, shadowless, approximately 24px high
 - Icon: 15–16px; disclosure chevron: 12px
-- Header gap: 4px; expanded body inset: 24px
+- Header gap: 4px; expanded tool-call details align with the row's own content
+  start and do not add a second horizontal inset. The collapse rail remains
+  available beside the expanded body. Thinking disclosures and subagent
+  topology nodes retain their dedicated hierarchy insets.
 - Chips: monospace `--text-2xs`, `--ds-tile-deep` fill (no border, D297), error hue for exit codes
 - Code, file list, match list and field blocks: `font-mono text-sm`,
   independently copyable, capped at 260px with internal scrolling

docs/spec/06-delivery/04-e2e-test-plan.md

@@ -2195,14 +2195,17 @@ identify the platform validation still needed.
   The header shows its localized processing label, elapsed time, and step count
   without an additional status capsule. When the turn settles, the automatic
   thinking disclosure closes, while a group or row touched by the user keeps
-  its chosen state. Expanded calls use transparent semantic activity rows with
-  an action icon, natural-language verb, monospace primary argument, and quiet
-  disclosure. The processing group uses the full assistant-column width, so a
-  short label or payload does not shrink expanded details into a content-sized
-  chip. Each expanded-content vertical rule is a pointer and keyboard-focusable
-  collapse control for its owning disclosure. Nested expansion shows output
-  before raw input in clamped scroll regions. Live partial output updates in
-  place. Reloaded rows preserve the tool name, arguments, result, and status.
+  its chosen state. A user-expanded tool call keeps its detail heading and
+  content aligned with the tool row rather than introducing another horizontal
+  indent; the collapse rail remains usable beside the body. Expanded calls use
+  transparent semantic activity rows with an action icon, natural-language verb,
+  monospace primary argument, and quiet disclosure. The processing group uses
+  the full assistant-column width, so a short label or payload does not shrink
+  expanded details into a content-sized chip. Each expanded-content vertical rule
+  is a pointer and keyboard-focusable collapse control for its owning disclosure.
+  Nested expansion shows output before raw input in clamped scroll regions. Live
+  partial output updates in place. Reloaded rows preserve the tool name,
+  arguments, result, and status.
 - **Specs linked**: `04-ux/01-ui-ia.md`,
   `04-ux/07-ui-design-system.md`, `04-ux/08-component-spec.md`,
   `04-ux/09-interaction-patterns.md`