refactor(frontend): the last pay-down, part 1 — three dead views deleted, editor rules shared, .page-container + .fs-input canon, rules-shared.css; a one-declaration CSS body is not a shape (#2903, milestone 299 step 5)

The derive queue said the biggest duplicate families were whole views:
TaskViewerView, UserManagementView and LogsView were imported nowhere — left
behind when tasks moved to the editor and users/logs became SettingsView
tabs. Deleted (rule 22). Note/TaskEditorView carried six identical scoped
rules -> editor-shared.css (the .tag-suggest-row gap the scoped copies
actually rendered wins). Three views wrapped the page under three names ->
.page-container in components.css. Three scoped input recipes -> the design
system fs-input recipe (snippet #2336), verbatim, in components.css; width/
box-sizing stay with the caller. The three rules panes share .pane and the
pane heading via rules-shared.css (the auth-shared pattern, #2852).

Ledger: a single-declaration CSS rule keeps its selector in its fingerprint,
so `color: var(--fs-text-tertiary)` under five different names is no longer
a five-file "identical body" family — the first pay-down found that most of
the 148 dup families were exactly this, and nobody would consolidate them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/SystemsSection.vue

@@ -176,7 +176,7 @@ async function confirmDelete() {
     <form v-if="showCreate" class="system-form" @submit.prevent="submitCreate">
       <input
         v-model="newName"
-        class="system-input"
+        class="fs-input system-input"
         placeholder="System name"
         aria-label="System name"
         autofocus
@@ -184,7 +184,7 @@ async function confirmDelete() {
       />
       <textarea
         v-model="newDescription"
-        class="system-textarea"
+        class="fs-input system-textarea"
         rows="2"
         placeholder="What is this subsystem responsible for? (optional)"
         aria-label="System description"
@@ -227,7 +227,7 @@ async function confirmDelete() {
           <form class="system-form system-form--inline" @submit.prevent="submitEdit(system)">
             <input
               v-model="editName"
-              class="system-input"
+              class="fs-input system-input"
               placeholder="System name"
               aria-label="System name"
               autofocus
@@ -235,7 +235,7 @@ async function confirmDelete() {
             />
             <textarea
               v-model="editDescription"
-              class="system-textarea"
+              class="fs-input system-textarea"
               rows="2"
               placeholder="Description (optional)"
               aria-label="System description"
@@ -372,18 +372,9 @@ async function confirmDelete() {
   border-radius: var(--fs-radius-lg);
 }
 .system-form--inline { padding: 0; background: none; border: none; flex: 1; }
-.system-input, .system-textarea {
-  padding: 0.4rem 0.6rem;
-  border: 1px solid var(--fs-border-color);
-  border-radius: var(--fs-radius-sm);
-  background: var(--fs-surface-page);
-  color: var(--fs-text-primary);
-  font-size: 0.875rem;
-  font-family: inherit;
-  box-sizing: border-box;
-  width: 100%;
-}
-.system-input:focus, .system-textarea:focus { outline: none; border-color: var(--fs-accent); }
+/* The input itself is the .fs-input canon (components.css); only the
+   layout remainder lives here. */
+.system-input, .system-textarea { box-sizing: border-box; width: 100%; }
 .system-textarea { resize: vertical; }
 
 .system-form-actions { display: flex; gap: 0.4rem; }