fix: clear the decorative flag when the upload dialog is handed a different file

The twin of the previous commit, with a sharper consequence. `decorative`
does not merely describe the previous image, it *exempts* it:
`validate-working-copy.ts`'s EVIDENCE_ALT_REQUIRED reads
`Asset.decorative`, so a flag inherited from a discarded divider lets a
meaningful diagram publish with no accessible name at all -- the check
passes rather than catching it. Stale alt text ships a wrong description;
stale `decorative` ships none.

Same terminal-state retry path: tick 장식용 for `divider.png`, have it
rejected, pick `sequence.png`, upload -- and `sequence.png` shipped as
decorative with `altText: undefined`.

Resetting it also re-enables the alt input, so the post-selection focus
call no longer has to ask whether it would land on a disabled control.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/features/tech-log/presentation/studio/components/asset-upload-dialog.tsx

@@ -200,9 +200,22 @@ export function AssetUploadDialog(props: Readonly<{
               // failure: "which file is this text describing" has one honest
               // answer per selection, and `submit()`'s ALT_REQUIRED refusal
               // makes the emptied field impossible to ignore.
+              //
+              // `decorative` is reset for the same reason and a sharper one.
+              // It does not merely describe the previous image, it *exempts*
+              // it: `validate-working-copy.ts`'s EVIDENCE_ALT_REQUIRED reads
+              // `Asset.decorative`, so a flag inherited from a discarded
+              // divider lets a meaningful diagram publish with no accessible
+              // name at all -- the check passes rather than catching it. Alt
+              // text riding along produces a wrong description; this produces
+              // none.
               setState({ kind: "IDLE" });
               setAltText("");
-              if (!decorative) altRef.current?.focus();
+              setDecorative(false);
+              // Unconditional now: the alt field is enabled again by the line
+              // above, so there is no longer a case where focusing it would
+              // land on a disabled control.
+              altRef.current?.focus();
             }}
           />
         </label>

tests/features/tech-log/asset-picker.test.tsx

@@ -1908,3 +1908,74 @@ test("the retry after a transport failure ships its own alt text, never the firs
     { altText: "시퀀스 다이어그램", filename: "sequence.png" },
   ]);
 });
+
+// The same defect as the alt-text one above, in the flag that *exempts* an
+// asset from needing alt text at all. Alt text surviving a file swap ships a
+// wrong description; `decorative` surviving one ships a meaningful image
+// marked as decorative -- `validate-working-copy.ts`'s EVIDENCE_ALT_REQUIRED
+// reads `Asset.decorative` and so passes it, and the image reaches publication
+// with no accessible name whatsoever. Worse than the bug it rides beside.
+test("picking a different file after a rejected upload clears the decorative flag too", async () => {
+  const user = userEvent.setup();
+  const forms: Array<{ decorative?: boolean; altText?: string; filename: string }> = [];
+  const gateway = uploadOnlyGateway(async (form) => {
+    forms.push({
+      decorative: form.decorative,
+      altText: form.altText,
+      filename: form.file.name,
+    });
+    return (forms.length === 1
+      ? { ...READY, managementStatus: "REJECTED" }
+      : READY) as never;
+  });
+  render(<AssetUploadDialog gateway={gateway} kind="IMAGE" onUploaded={() => {}} onClose={() => {}} />);
+
+  chooseFile(new File(["a"], "divider.png", { type: "image/png" }));
+  await user.click(screen.getByLabelText("장식용 이미지 (대체 텍스트 없음)"));
+  await user.click(screen.getByRole("button", { name: "업로드" }));
+  await waitFor(() =>
+    assert.equal(
+      screen.getByRole("status", { name: "업로드 상태" }).textContent,
+      "서버 검증에서 거절되어 사용할 수 없습니다.",
+    ),
+  );
+  assert.deepEqual(forms, [
+    { decorative: true, altText: undefined, filename: "divider.png" },
+  ]);
+
+  // A meaningful diagram is chosen next. It must not inherit the divider's
+  // "no alt text needed" exemption.
+  chooseFile(new File(["b"], "sequence.png", { type: "image/png" }));
+
+  assert.equal(
+    (screen.getByLabelText("장식용 이미지 (대체 텍스트 없음)") as HTMLInputElement).checked,
+    false,
+  );
+  // The alt field is re-enabled by the same reset -- while `decorative` was
+  // still set it was `disabled`, so a cleared-but-disabled field would be a
+  // dead end.
+  assert.equal((screen.getByLabelText("대체 텍스트") as HTMLInputElement).disabled, false);
+
+  // And it is enforced: uploading now refuses instead of publishing an
+  // unnamed image.
+  await user.click(screen.getByRole("button", { name: "업로드" }));
+  assert.equal(
+    screen.getByRole("status", { name: "업로드 상태" }).textContent,
+    "대체 텍스트를 입력하거나 장식용으로 표시하세요.",
+  );
+  assert.equal(forms.length, 1);
+
+  await user.type(screen.getByLabelText("대체 텍스트"), "시퀀스 다이어그램");
+  await user.click(screen.getByRole("button", { name: "업로드" }));
+  await waitFor(() =>
+    assert.equal(
+      screen.getByRole("status", { name: "업로드 상태" }).textContent,
+      "업로드했습니다.",
+    ),
+  );
+  assert.deepEqual(forms[1], {
+    decorative: false,
+    altText: "시퀀스 다이어그램",
+    filename: "sequence.png",
+  });
+});