Resolve duplicate CSS selectors reported by Stylelint (Stirling-Tools#7212)

Fixes Stirling-Tools#7189

Consolidates all 29 `no-duplicate-selectors` violations across 18
stylesheets by merging later duplicate rule blocks into the first
occurrence. Where duplicates had conflicting values, the cascade-winning
(later) value was kept, so computed styles are unchanged.

Also:
- Adds `frontend/stylelint.config.mjs` with only
`no-duplicate-selectors` enabled (Prettier and the theme linter own
everything else).
- Adds a `frontend:lint:css` task, wired into `task frontend:lint` as a
blocking check so regressions can't creep back in.
- Lints all first-party CSS (`editor/**/*.css`, so `public/css` and any
future non-`src` stylesheets are covered too), excluding only the
vendored `cookieconsent.css` and build output via `ignoreFiles`. This
surfaced and fixed 5 additional duplicate selectors in
`cookieconsentCustomisation.css` that weren't in the original issue
report.

Note: `portal/views/Sources.css` goes beyond dedup — the whole
`.portal-sources__connections*` block is deleted as dead code
(unreferenced since the S3 connections redesign in Stirling-Tools#6965; only
`-actions` in it was an actual duplicate).

🤖 Generated with [Claude Code](https://claude.ai/code)

Author: EthanHealy01

.taskfiles/frontend.yml

@@ -263,6 +263,16 @@ tasks:
       - task: lint:eslint
       - task: lint:dpdm
       - task: lint:colors
+      - task: lint:css
+
+  lint:css:
+    desc: "Lint stylesheets for duplicate selectors"
+    deps: [install]
+    cmds:
+      # Covers the whole editor tree, including the portal/processor layer and
+      # public/css. Vendored CSS and build output are excluded via ignoreFiles
+      # in stylelint.config.mjs.
+      - npx stylelint "editor/**/*.css"
 
   lint:colors:
     desc: "Enforce theme tokens — no hardcoded colours or raw primitives in components"

frontend/editor/public/css/cookieconsentCustomisation.css

@@ -130,37 +130,47 @@
   opacity: 0 !important; /* Keep invisible but functional */
 }
 
+/* Track: flat fill in both themes, no outline ring or border */
 #cc-main .toggle__icon {
   display: flex !important;
   align-items: center !important;
   justify-content: flex-start !important;
+  background: var(--cc-toggle-off-bg) !important;
+  border: none !important;
+  box-shadow: none !important;
+  transition: background-color 150ms ease !important;
 }
 
+/* Thumb: small plain circle, vertically centred, no drop shadow */
 #cc-main .toggle__icon-circle {
   display: block !important;
   position: absolute !important;
-  transition: transform 0.25s ease !important;
+  width: 14px !important;
+  height: 14px !important;
+  top: 3px !important;
+  left: 2.5px !important;
+  box-shadow: none !important;
+  transition:
+    transform 150ms ease,
+    background-color 150ms ease !important;
 }
 
+/* Mantine switches have no check/cross glyph inside the thumb */
 #cc-main .toggle__icon-on,
 #cc-main .toggle__icon-off {
-  display: flex !important;
+  display: none !important;
   align-items: center !important;
   justify-content: center !important;
   position: absolute !important;
   width: 100% !important;
   height: 100% !important;
 }
 
-/* Ensure toggles are visible in both themes */
-#cc-main .toggle__icon {
-  background: var(--cc-toggle-off-bg) !important;
-  border: 1px solid var(--cc-toggle-off-bg) !important;
-}
-
+/* Checked track visible in both themes, same flat Mantine look */
 #cc-main .section__toggle:checked ~ .toggle__icon {
   background: var(--cc-toggle-on-bg) !important;
-  border: 1px solid var(--cc-toggle-on-bg) !important;
+  border: none !important;
+  box-shadow: none !important;
 }
 
 /* Ensure toggle text is visible */
@@ -226,18 +236,6 @@
   border-radius: 1000px !important;
 }
 
-/* Track: flat fill, no outline ring or border */
-#cc-main .toggle__icon {
-  border: none !important;
-  box-shadow: none !important;
-  transition: background-color 150ms ease !important;
-}
-
-#cc-main .section__toggle:checked ~ .toggle__icon {
-  border: none !important;
-  box-shadow: none !important;
-}
-
 /* Always-enabled categories = Mantine disabled switch (must out-prioritise
    the !important checked-track rule above) */
 #cc-main .section__toggle:checked:disabled ~ .toggle__icon {
@@ -250,25 +248,7 @@
   cursor: not-allowed !important;
 }
 
-/* Thumb: small plain circle, vertically centred, no drop shadow */
-#cc-main .toggle__icon-circle {
-  width: 14px !important;
-  height: 14px !important;
-  top: 3px !important;
-  left: 2.5px !important;
-  box-shadow: none !important;
-  transition:
-    transform 150ms ease,
-    background-color 150ms ease !important;
-}
-
 /* Checked thumb travel: 38 − 14 − 2.5 = 21.5px end position */
 #cc-main .section__toggle:checked ~ .toggle__icon .toggle__icon-circle {
   transform: translateX(19px) !important;
 }
-
-/* Mantine switches have no check/cross glyph inside the thumb */
-#cc-main .toggle__icon-on,
-#cc-main .toggle__icon-off {
-  display: none !important;
-}

frontend/editor/src/core/components/fileEditor/FileEditor.module.css

@@ -320,11 +320,6 @@
   color: var(--c-text-muted); /* subtitle text */
 }
 
-/* Light mode selected header stroke override */
-:global([data-mantine-color-scheme="light"]) .card[data-selected="true"] {
-  outline-color: var(--c-primary);
-}
-
 /* =========================
    Add File Card Styles
    ========================= */

frontend/editor/src/core/components/filesPage/FilesPage.css

@@ -156,6 +156,11 @@
   flex-shrink: 0;
   flex-wrap: wrap;
   min-height: 3rem;
+  /* Safety net - the content should always fit thanks to the shrink rules on
+     `.files-page-toolbar-actions` below, but if a future addition ever breaks
+     that, this stops the action group bleeding into sibling areas (notably the
+     details panel on the right). */
+  overflow-x: hidden;
 }
 
 .files-page-toolbar-info {
@@ -210,13 +215,6 @@
 .files-page-toolbar-actions .mantine-SegmentedControl-root {
   flex-shrink: 0;
 }
-/* Clip overflow on the toolbar itself as a safety net - the content
-   should always fit thanks to the rules above, but if a future addition
-   ever breaks that, this prevents the action group from bleeding into
-   sibling areas (notably the details panel on the right). */
-.files-page-toolbar {
-  overflow-x: hidden;
-}
 
 .files-page-toolbar-divider {
   width: 1px;
@@ -1319,9 +1317,6 @@
     gap: 0.3rem;
     flex-wrap: nowrap;
   }
-  .files-page-search {
-    flex: 1 1 100%;
-  }
   .files-page-breadcrumbs {
     font-size: 0.85rem;
     flex-wrap: nowrap;

frontend/editor/src/core/components/shared/FileSidebar.css

@@ -447,19 +447,14 @@
 }
 
 .file-sidebar-section-header {
+  position: relative;
   display: flex;
   align-items: center;
   justify-content: space-between;
   gap: 8px;
-  padding: 12px 14px 6px 14px;
+  padding: 10px 14px 6px 14px;
   margin: 4px 0 0 0;
-}
-
-.file-sidebar-section-header {
-  position: relative;
   border-top: 1px solid var(--c-border-subtle);
-  padding-top: 10px;
-  margin-top: 4px;
   flex-shrink: 0;
 }
 

frontend/editor/src/core/components/shared/FileSidebarFileItem.css

@@ -56,12 +56,6 @@
   pointer-events: auto;
 }
 
-/* Always reserve space for action buttons so file name truncation dots (...)
-   never bleed under action buttons or overlap their outline/focus box. */
-.file-sidebar-file-info {
-  padding-right: 3.75rem;
-}
-
 .file-sidebar-file-item:hover:not(.selected) {
   background-color: color-mix(in srgb, var(--c-primary) 6%, transparent);
 }
@@ -173,6 +167,9 @@
 .file-sidebar-file-info {
   flex: 1;
   min-width: 0;
+  /* Always reserve space for action buttons so file name truncation dots (...)
+     never bleed under action buttons or overlap their outline/focus box. */
+  padding-right: 3.75rem;
 }
 
 .file-sidebar-file-name {