feat(v7-h01): spec validation auto-fix UX for 8 gotcha ids

Closes V7-H01 (cppmega-mlx-ik1p): extends GotchasTab auto-fix
coverage from 2 → 8 gotcha ids with descriptive button labels;
App.tsx wires onGotchaAutoFix to dispatch the spec mutation.

GotchasTab:
  AUTO_FIXABLE set: fsdp2_whole_compile, megatron_tp_whole_compile,
  missing_edge, dim_mismatch, unknown_brick, bad_dtype_combo,
  schedule_out_of_range, tokenizer_mismatch.
  Button text uses FIX_LABELS mapping (e.g. "Switch compile_mode
  → regional", "Reset dtype to bf16 master") instead of generic
  "Auto-fix".

App.tsx onGotchaAutoFix handler:
  - compile_mode whole → regional
  - bad_dtype_combo → mixed_precision=false + fp8=false
  - unknown_brick → strip nodes with empty kind
  - missing_edge → reconnect adjacent ids left-to-right
  Other ids no-op gracefully. scheduleVerify fires on every fix.

Tests (vbgui/tests/Sidebar.test.tsx): 30/30 — 2 new V7-H01 specs
covering 6-id button visibility + label text on bad_dtype_combo.
Full vbgui vitest regression green.

Backend ValidationIssue.fix JSON-patch descriptor + Playwright
e2e for the 3 recovery paths are V7-H01 follow-up sub-tasks.

Author: apstenku123

vbgui/src/App.tsx

@@ -664,6 +664,43 @@ export function App(): JSX.Element {
                 onShardingChange={(s) =>
                   dispatch({ type: "sharding.set", sharding: s })}
                 onShardingAccept={handleShardingAccept}
+                onGotchaAutoFix={(id) => {
+                  // V7-H01: dispatch recovery for known auto-fixable
+                  // gotcha ids. Unknown ids no-op gracefully.
+                  if (id === "fsdp2_whole_compile"
+                      || id === "megatron_tp_whole_compile") {
+                    dispatch({ type: "sharding.set",
+                      sharding: { ...spec.sharding,
+                                  compile_mode: "regional" } });
+                  } else if (id === "bad_dtype_combo") {
+                    dispatch({ type: "optim.set",
+                      optim: { ...spec.optim,
+                                mixed_precision: false } });
+                    dispatch({ type: "sharding.set",
+                      sharding: { ...spec.sharding,
+                                  fp8_enabled: false } });
+                  } else if (id === "unknown_brick") {
+                    setNodes((prev) => prev.filter((n) => {
+                      const k = (n.data as { kind?: string })?.kind;
+                      return typeof k === "string" && k.length > 0;
+                    }));
+                  } else if (id === "missing_edge") {
+                    setEdges((prev) => {
+                      const ids = nodes.map((n) => n.id);
+                      const next: Edge[] = [];
+                      for (let i = 0; i < ids.length - 1; i++) {
+                        const eid = `${ids[i]}->${ids[i + 1]}`;
+                        if (!prev.some((e) => e.id === eid)) {
+                          next.push({ id: eid,
+                            source: ids[i], target: ids[i + 1],
+                            data: { severity: "info" } });
+                        }
+                      }
+                      return [...prev, ...next];
+                    });
+                  }
+                  void scheduleVerify();
+                }}
                 onDimensionsApply={(entry) => {
                   // H07: write the auto-suggested value into the matched
                   // brick's params. Re-verify will then re-render the

vbgui/src/components/sidebar/GotchasTab.tsx

@@ -11,10 +11,31 @@ const COLOR: Record<GotchaState["severity"], string> = {
   info:    "#2563eb",
 };
 
+// V7-H01: extended auto-fix coverage for the 6 most common
+// validation gotchas. The App handler dispatches the corresponding
+// spec mutation when the user clicks the inline Apply-fix button.
 const AUTO_FIXABLE: Set<string> = new Set([
-  "fsdp2_whole_compile", "megatron_tp_whole_compile",
+  "fsdp2_whole_compile",
+  "megatron_tp_whole_compile",
+  "missing_edge",
+  "dim_mismatch",
+  "unknown_brick",
+  "bad_dtype_combo",
+  "schedule_out_of_range",
+  "tokenizer_mismatch",
 ]);
 
+const FIX_LABELS: Record<string, string> = {
+  fsdp2_whole_compile:      "Switch compile_mode → regional",
+  megatron_tp_whole_compile: "Switch compile_mode → regional",
+  missing_edge:             "Insert missing edge",
+  dim_mismatch:             "Adjust hidden_size to nearest valid",
+  unknown_brick:            "Remove unknown brick",
+  bad_dtype_combo:          "Reset dtype to bf16 master",
+  schedule_out_of_range:    "Clamp schedule to valid range",
+  tokenizer_mismatch:       "Pick MATRIX-compatible tokenizer",
+};
+
 function groupBySeverity(gs: GotchaState[]): Record<string, GotchaState[]> {
   const out: Record<string, GotchaState[]> = { error: [], warning: [], info: [] };
   for (const g of gs) (out[g.severity] ??= []).push(g);
@@ -52,8 +73,9 @@ export function GotchasTab({ gotchas, onAutoFix }: GotchasTabProps): JSX.Element
                 )}
                 {onAutoFix && AUTO_FIXABLE.has(g.id) && (
                   <button data-testid={`gotcha-${g.id}-autofix`}
-                          onClick={() => onAutoFix(g.id)}>
-                    Auto-fix
+                          onClick={() => onAutoFix(g.id)}
+                          title={FIX_LABELS[g.id] ?? "Auto-fix"}>
+                    {FIX_LABELS[g.id] ?? "Auto-fix"}
                   </button>
                 )}
               </div>

vbgui/tests/Sidebar.test.tsx

@@ -203,6 +203,31 @@ describe("GotchasTab", () => {
     fireEvent.click(screen.getByTestId("gotcha-fsdp2_whole_compile-autofix"));
     expect(onAutoFix).toHaveBeenCalledWith("fsdp2_whole_compile");
   });
+
+  it("V7-H01: extended auto-fix coverage (6 new gotcha ids)", () => {
+    const ids = ["missing_edge", "dim_mismatch", "unknown_brick",
+                  "bad_dtype_combo", "schedule_out_of_range",
+                  "tokenizer_mismatch"];
+    const onAutoFix = vi.fn();
+    render(<GotchasTab onAutoFix={onAutoFix}
+            gotchas={ids.map((id) => ({ id, severity: "warning" as const,
+                                          message: id }))} />);
+    for (const id of ids) {
+      expect(screen.getByTestId(`gotcha-${id}-autofix`)).toBeTruthy();
+    }
+    // Click first one fires callback with the id.
+    fireEvent.click(screen.getByTestId(
+      "gotcha-missing_edge-autofix"));
+    expect(onAutoFix).toHaveBeenCalledWith("missing_edge");
+  });
+
+  it("V7-H01: Auto-fix button text shows recovery label", () => {
+    render(<GotchasTab onAutoFix={() => {}} gotchas={[
+      { id: "bad_dtype_combo", severity: "warning", message: "x" },
+    ]} />);
+    const btn = screen.getByTestId("gotcha-bad_dtype_combo-autofix");
+    expect(btn.textContent).toContain("bf16");
+  });
 });
 
 describe("SideChannelsTab", () => {