P2R-02 slice 2: Sources tab — list, new/edit form, delete, Run-now

Sources tab now lists every source group on the host with per-row
counts (used-by-N-schedules, snapshot count by tag), the v4
conflict tag (keep-* dimension that has no compatible cadence),
and Run-now / Edit / Delete actions. Run-now reuses the existing
HTMX-aware /hosts/{id}/source-groups/{gid}/run handler.

New /hosts/{id}/sources/new and /sources/{gid}/edit form: name +
includes/excludes textareas + the 3×2 keep-* retention grid +
retry-on-offline knobs. Server-side validation re-renders with the
operator's input intact; the inline conflict banner shows above the
retention grid when ConflictDimension is set.

Delete blocks (UI + server) when the group is referenced by any
schedule. Every successful mutation calls pushScheduleSetAsync so
an online agent re-arms within seconds.

Adds .src-row and .keep-cell to input.css for the row + retention
grid layout.

web/styles/input.css

@@ -186,6 +186,32 @@
   .host-row.clickable > .row-link { pointer-events: auto; }
   .host-row.clickable > .row-action { pointer-events: auto; }
 
+  /* ---------- source-group rows (Sources tab) ---------- */
+  .src-row {
+    display: grid; align-items: center;
+    grid-template-columns: 1fr auto;
+    column-gap: 18px;
+    padding: 14px 18px;
+  }
+
+  /* ---------- retention 3×2 keep-* grid (source-group edit) ---------- */
+  .keep-cell {
+    background: var(--bg);
+    border: 1px solid var(--line-soft);
+    border-radius: 5px;
+    padding: 9px 11px;
+    display: flex; flex-direction: column; gap: 4px;
+  }
+  .keep-cell label {
+    font-size: 10.5px; text-transform: uppercase; letter-spacing: 0.08em;
+    color: var(--ink-fade);
+  }
+  .keep-cell input {
+    background: transparent; border: none; outline: none;
+    font-family: 'JetBrains Mono', monospace; font-size: 14px;
+    color: var(--ink); padding: 0; width: 100%;
+  }
+
   /* ---------- log viewer ---------- */
   .log {
     background: var(--bg); border: 1px solid var(--line-soft);