feat(git): add stash push with optional paths and per-file scope

The stash push feature now supports limiting the stash to
selected files via an optional paths parameter.
The UI passes file paths to stash_push and adds a
per-file context menu for scoped stash operations.

- Extend stash API to accept optional paths for scoped stashes
- Implement per-file stash actions via a status panel context menu
- Update tests and docs to reflect scoped stash behavior

src/app.css

@@ -2327,6 +2327,7 @@
   .branch-context-menu,
   .history-context-menu,
   .explorer-context-menu,
+  .status-context-menu,
   .repo-tab-context-menu {
     z-index: 120;
     display: grid;
@@ -2346,11 +2347,102 @@
   }
   .history-context-menu { position: absolute; }
   .explorer-context-menu,
+  .status-context-menu,
   .repo-tab-context-menu { position: fixed; }
 
+  .status-context-menu {
+    width: min(280px, calc(100vw - 16px));
+    padding: 6px;
+    border-color: color-mix(in srgb, var(--color-border) 78%, #5a8cf8);
+    background:
+      linear-gradient(180deg, rgba(90,140,248,0.045), transparent 70px),
+      var(--color-surface-solid);
+  }
+
+  .status-context-label {
+    display: grid;
+    grid-template-columns: 32px minmax(0, 1fr) auto;
+    align-items: center;
+    gap: 9px;
+    min-width: 0;
+    margin: -1px -1px 5px;
+    padding: 8px 8px 10px;
+    border-bottom: 1px solid var(--color-border-subtle);
+  }
+
+  .status-context-object-icon,
+  .status-context-action-icon {
+    display: inline-grid;
+    place-items: center;
+    flex: 0 0 auto;
+    color: #83adff;
+    background: rgba(90,140,248,0.12);
+    border: 1px solid rgba(90,140,248,0.2);
+  }
+
+  .status-context-object-icon {
+    width: 32px;
+    height: 32px;
+    border-radius: 7px;
+  }
+
+  .status-context-object-copy,
+  .status-context-action-copy {
+    display: grid;
+    min-width: 0;
+  }
+
+  .status-context-kind {
+    margin-bottom: 2px;
+    color: var(--color-ink-faint);
+    font-size: 8.5px;
+    font-weight: 800;
+    letter-spacing: .1em;
+    line-height: 1;
+    text-transform: uppercase;
+  }
+
+  .status-context-object-copy > strong {
+    overflow: hidden;
+    color: var(--color-ink);
+    font-size: 12.5px;
+    line-height: 1.25;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+  }
+
+  .status-context-path {
+    display: flex;
+    align-items: center;
+    gap: 4px;
+    min-width: 0;
+    margin-top: 2px;
+    overflow: hidden;
+    color: var(--color-ink-faint);
+    font: 9.5px/1.2 var(--font-mono);
+    text-overflow: ellipsis;
+    white-space: nowrap;
+  }
+
+  .status-context-path svg { flex: 0 0 auto; }
+
+  .status-context-count {
+    display: inline-grid;
+    place-items: center;
+    min-width: 20px;
+    height: 20px;
+    padding: 0 5px;
+    border: 1px solid rgba(90,140,248,0.18);
+    border-radius: 5px;
+    color: #83adff;
+    background: rgba(90,140,248,0.1);
+    font: 700 9.5px/1 var(--font-mono);
+  }
+
   .branch-context-menu button,
   .history-context-menu button,
   .explorer-context-menu button,
+  .status-context-menu button,
   .repo-tab-context-menu button {
     display: flex;
     align-items: center;
@@ -2368,15 +2460,52 @@
     text-align: left;
   }
 
+  .status-context-menu button {
+    min-height: 42px;
+    gap: 9px;
+    padding: 6px 7px;
+  }
+
+  .status-context-action-icon {
+    width: 26px;
+    height: 26px;
+    border-color: transparent;
+    border-radius: 6px;
+    background: transparent;
+    color: var(--color-ink-dim);
+  }
+
+  .status-context-action-copy { gap: 1px; }
+  .status-context-action-copy strong {
+    color: var(--color-ink-muted);
+    font-size: 11.5px;
+    line-height: 1.25;
+  }
+  .status-context-action-copy span {
+    color: var(--color-ink-faint);
+    font-size: 9.5px;
+    font-weight: 500;
+    line-height: 1.25;
+  }
+
   .branch-context-menu button:hover:not(:disabled),
   .history-context-menu button:hover:not(:disabled),
   .explorer-context-menu button:hover:not(:disabled),
+  .status-context-menu button:hover:not(:disabled),
   .repo-tab-context-menu button:hover:not(:disabled) {
     border-color: var(--color-border-subtle);
     background: rgba(255,255,255,0.06);
     color: var(--color-ink);
   }
 
+  .status-context-menu button:hover:not(:disabled) .status-context-action-icon {
+    color: #9bbcff;
+    background: rgba(90,140,248,0.1);
+  }
+  .status-context-menu button:hover:not(:disabled) .status-context-action-copy strong {
+    color: var(--color-ink);
+  }
+
   .branch-context-menu .menu-separator,
   .history-context-menu .menu-separator,
   .repo-tab-context-menu .menu-separator {
@@ -2398,6 +2527,7 @@
   .branch-context-menu button:disabled,
   .history-context-menu button:disabled,
   .explorer-context-menu button:disabled,
+  .status-context-menu button:disabled,
   .repo-tab-context-menu button:disabled {
     cursor: not-allowed;
     opacity: 0.48;
@@ -7651,6 +7781,7 @@ input:focus, textarea:focus, select:focus { box-shadow: 0 0 0 3px color-mix(in s
     grid-template-columns: minmax(0, 1fr);
     grid-template-rows: minmax(0, 1fr) 25px minmax(0, 1fr);
   }
+
   .status-flow-divider::before {
     inset-block: auto;
     inset-inline: 0;