Merge #761 feat(picker): New folder button for Create New's custom folder picker

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/web/public/session-ui.js

@@ -4051,6 +4051,7 @@ Object.assign(CodemanApp.prototype, {
       title: 'Choose the folder to create the case in',
       initialPath: input.value.trim(),
       directoriesOnly: true,
+      allowNewFolder: true,
       onSelect: (path) => {
         input.value = path;
         this.updateNewCasePathPreview();

src/web/public/styles.css

@@ -16016,8 +16016,10 @@ body.touch-device.cjk-input-visible .main {
   white-space: nowrap;
 }
 
+/* An ordinary status fits one line; a refusal may not, and it must be readable whole. */
 .path-picker-status.error {
   color: var(--danger, #ef4444);
+  white-space: normal;
 }
 
 .path-picker-list {

src/web/routes/file-routes.ts

@@ -1500,7 +1500,9 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort & Even
     }
     // The cases directories (shared, and the caller's own in multi-user mode) are what GET /api/cases lists as
     // local cases: a folder made there is a case with no scaffold, which Link then refuses by name and which
-    // deleting would take the linked folder with. A case there is made through Add Case > New Case.
+    // deleting would take the linked folder with. A case there is made through Add Case > Create New with no
+    // custom folder. The refusal has to read right from both pickers that offer New folder: a Create New user
+    // is already on that tab, with the custom folder ticked.
     const casesDirs = await Promise.all(
       [...new Set([CASES_DIR, resolveCasesDir(getAuthUser(req))])].map((dir) =>
         fs.realpath(dir).catch(() => resolve(dir))
@@ -1510,7 +1512,7 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort & Even
       reply.code(400);
       return createErrorResponse(
         ApiErrorCode.INVALID_INPUT,
-        'This is a cases folder: every folder in it is a case. Use Add Case > New Case to make one there.'
+        'This is a cases folder: every folder in it is a case. Pick a folder outside it, or make the case with Add Case > Create New (no custom folder).'
       );
     }
     // Like browse, a file is not a place to create in.