fix(cases): never let a path decide whether a refused clone empties the folder

git's refusal quotes the destination, so a folder named openssl or rustls
classified as HOST_UNREACHABLE and the cleanup emptied it. The cleanup now
tests git's own text, DESTINATION_EXISTS is matched first, and ssl/tls are
matched as words. Also: a test for the Docker refusal on the default branch,
the route JSDoc and constant comment, and the folder copy (empty, or new).

src/web/public/index.html

@@ -3658,7 +3658,7 @@
             </div>
             <div class="form-row" id="cloneCustomPathToggleRow">
               <label class="checkbox-row"><input type="checkbox" id="cloneCustomPathToggle" onchange="app.toggleCloneCustomPath()"> 📁 Clone into a custom folder</label>
-              <span class="form-hint">By default the clone goes under ~/codeman-cases. Choose a folder and the repository is cloned into that folder itself (it must be empty); it is listed like any other case, and deleting the case only unlinks it (your files stay).</span>
+              <span class="form-hint">By default the clone goes under ~/codeman-cases. Choose a folder and the repository is cloned into that folder itself (an empty folder, or one that does not exist yet); it is listed like any other case, and deleting the case only unlinks it (your files stay).</span>
             </div>
             <div class="form-row" id="cloneCustomPathRow" style="display:none">
               <label>Folder</label>
@@ -3666,7 +3666,7 @@
                 <input type="text" id="cloneCasePath" placeholder="~/projects" autocomplete="off" autocapitalize="off" autocorrect="off" spellcheck="false" oninput="app.updateCloneCasePathPreview()">
                 <button type="button" class="btn path-input-browse" onclick="app.openCloneCasePathPicker()">Browse&hellip;</button>
               </div>
-              <span class="form-hint" id="cloneCasePathPreview">Pick the empty folder to clone into.</span>
+              <span class="form-hint" id="cloneCasePathPreview">Pick an empty folder, or one that does not exist yet, to clone into.</span>
             </div>
             <div class="form-row">
               <label>Branch or Tag (optional)</label>

src/web/public/session-ui.js

@@ -4159,7 +4159,7 @@ Object.assign(CodemanApp.prototype, {
     const hint = document.getElementById('cloneCasePathPreview');
     if (!hint) return;
     const target = this._cloneTargetPath();
-    hint.textContent = target ? `Will clone into: ${target}` : 'Pick the empty folder to clone into.';
+    hint.textContent = target ? `Will clone into: ${target}` : 'Pick an empty folder, or one that does not exist yet, to clone into.';
   },
 
   openCloneCasePathPicker() {

src/web/routes/case-routes.ts

@@ -149,12 +149,13 @@ const APP_VERSION = (() => {
  * would copy another user's workspace into the caller's own (the same escape
  * `/api/cases/link` is admin-only for).
  */
-const DOCKER_CLONE_REFUSAL =
-  'Cloning is not available into a folder inside a Docker case workspace: a container can write there, and git would run the new repository’s hooks and filters on this machine. Clone outside the workspace and link it, or clone from inside the container.';
-
 const LOCAL_CLONE_ADMIN_ONLY =
   'Cloning from a local path is admin-only in multi-user mode. Use a repository URL instead.';
 
+/** Refusal text for a clone at or inside a Docker case workspace (git would run its hooks on the host). */
+const DOCKER_CLONE_REFUSAL =
+  'Cloning is not available into a folder inside a Docker case workspace: a container can write there, and git would run the new repository’s hooks and filters on this machine. Clone outside the workspace and link it, or clone from inside the container.';
+
 /**
  * Whether a clone or preflight must run with git's credential helpers cleared:
  * a non-admin in multi-user mode. Every user's git runs as the one server
@@ -666,7 +667,8 @@ export function registerCaseRoutes(
    * request died mid-clone still sees the case appear over SSE when git finishes.
    *
    * Deliberately NOT admin-gated in multi-user mode: unlike `/api/cases/link`,
-   * this writes only inside the caller's own `resolveCasesDir`. Two things would
+   * this writes only inside the caller's own `resolveCasesDir`, EXCEPT with a `path` (a custom folder,
+   * registered as a linked case in the shared registry), which is admin-only like Link Existing. Two things would
    * otherwise read through that boundary: a `local`-transport source (refused for
    * non-admins) and the server account's git credential helpers, which every user
    * shares (cleared for non-admins, see `cloneWithoutCredentialHelpers`).