newOS4 v4.6.18: nginx dav trailing-slash semantics

Discovered by dav-health-check.sh E2E (10/10 pass now):
- nginx dav module REQUIRES trailing slash on MKCOL (no-slash → 409)
  and on directory DELETE (no-slash → 409/404); existing dir + slash
  MKCOL → 405 (the real 'already exists' signal)
- _normalizeRemotePath now PRESERVES trailing slashes (collection ops)
- _ensureDir MKCOLs with trailing slash
- _deleteFile retries with slash on 409/404 (collection delete)
- health-check expectations corrected (405 = existing, slash required)

1 files changed, 20 insertions, 4 deletions

diff --git a/modules/ext/webdav.js b/modules/ext/webdav.js
index 5bcc4ee..e989ac9 100644
--- a/modules/ext/webdav.js
+++ b/modules/ext/webdav.js
@@ -194,14 +194,19 @@ class WebDAVModule {
         }
         p = p.split('?')[0].split('#')[0];
         if (!p.startsWith('/')) p = '/' + p;
-        // Collapse duplicate slashes and resolve '..' / '.' segments
+        // Collapse duplicate slashes and resolve '..' / '.' segments.
+        // PRESERVE a trailing slash — nginx's dav module needs it for
+        // collection operations (MKCOL/DELETE on directories).
+        const trailing = /\/+$/.test(p);
         const out = [];
         for (const seg of p.split('/')) {
             if (seg === '' || seg === '.') continue;
             if (seg === '..') { out.pop(); continue; }
             out.push(seg);
         }
-        return '/' + out.join('/');
+        let res = '/' + out.join('/');
+        if (trailing && res !== '/') res += '/';
+        return res;
     }
 
     _absoluteUrl(remotePath) {
@@ -414,7 +419,10 @@ class WebDAVModule {
         for (let i = deepest; i < segments.length; i++) {
             current += '/' + segments[i];
             try {
-                const attempt = await this._webdavRequest('MKCOL', current);
+                // nginx dav requires a TRAILING SLASH on MKCOL for the
+                // collection itself (no-slash → 409 'conflict'). Verified
+                // live 2026-10-02: no-slash 409, with-slash 201.
+                const attempt = await this._webdavRequest('MKCOL', current + '/');
                 if (attempt.ok || attempt.status === 405 || attempt.status === 301 || attempt.status === 302) created = true;
             } catch (e) { /* ignore — component may exist */ }
         }
@@ -422,8 +430,16 @@ class WebDAVModule {
     }
     
     async _deleteFile(remotePath) {
+        const p = this._normalizeRemotePath(remotePath);
         const resp = await this._webdavRequest('DELETE', remotePath);
-        return resp.ok || resp.status === 204 || resp.status === 404;
+        if (resp.ok || resp.status === 204 || resp.status === 404) return true;
+        // nginx dav needs a trailing slash to delete a COLLECTION; a no-slash
+        // DELETE on a directory returns 409/404. Retry with slash.
+        if ((resp.status === 409 || resp.status === 404) && !p.endsWith('/')) {
+            const retry = await this._webdavRequest('DELETE', p + '/');
+            return retry.ok || retry.status === 204 || retry.status === 404;
+        }
+        return false;
     }
     
     async _cleanupRetention() {