feat(zero): render Zero Amount header and OOB-swap on every mutation

Single large number on /, Planned + Applied pair on /month/YYYY-MM,
both colour-coded (green at zero, amber positive, red negative).
Every mutation route (add, delete, month entry update) appends the
zero widget to its response with hx-swap-oob so totals stay in sync
without a full page reload. An _append_oob helper replaces the ad-hoc
string concatenation the target card was already using.

Refs #7

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/quartermaster/routes.py

@@ -57,12 +57,27 @@ def _render_target(request: Request, db: Session) -> HTMLResponse:
     )
 
 
+def _render_zero(request: Request, db: Session) -> HTMLResponse:
+    zero = service.budget_zero(db)
+    return templates.TemplateResponse(
+        request,
+        "partials/budget_zero.html",
+        {"zero": zero, "tone": service.zero_tone(zero)},
+    )
+
+
+def _append_oob(base: HTMLResponse, *extras: HTMLResponse) -> HTMLResponse:
+    body = base.body.decode() + "".join(e.body.decode() for e in extras)
+    return HTMLResponse(body)
+
+
 @router.get("/", response_class=HTMLResponse)
 def index(request: Request, db: Session = Depends(get_session)) -> HTMLResponse:
     sections = [_section_view(db, s) for s in Section]
     target = service.get_debt_target(db)
     debt_minimums = service.list_entries(db, Section.debt_minimum)
     current_ym = month_service.current_year_month()
+    zero = service.budget_zero(db)
     return templates.TemplateResponse(
         request,
         "index.html",
@@ -72,6 +87,8 @@ def index(request: Request, db: Session = Depends(get_session)) -> HTMLResponse:
             "debt_minimums": debt_minimums,
             "current_year_month": current_ym,
             "all_months": month_service.list_months(db),
+            "zero": zero,
+            "tone": service.zero_tone(zero),
         },
     )
 
@@ -90,10 +107,10 @@ def create_entry(
     parsed = _parse_amount(amount)
     service.add_entry(db, section, clean_name, parsed)
     response = _render_section(request, db, section)
+    extras: list[HTMLResponse] = [_render_zero(request, db)]
     if section == Section.debt_minimum:
-        target_html = _render_target(request, db).body.decode()
-        response = HTMLResponse(response.body.decode() + target_html)
-    return response
+        extras.append(_render_target(request, db))
+    return _append_oob(response, *extras)
 
 
 @router.delete("/entries/{entry_id}", response_class=HTMLResponse)
@@ -106,10 +123,10 @@ def remove_entry(
     if entry is None:
         raise HTTPException(status_code=404, detail="entry not found")
     response = _render_section(request, db, entry.section)
+    extras: list[HTMLResponse] = [_render_zero(request, db)]
     if entry.section == Section.debt_minimum:
-        target_html = _render_target(request, db).body.decode()
-        response = HTMLResponse(response.body.decode() + target_html)
-    return response
+        extras.append(_render_target(request, db))
+    return _append_oob(response, *extras)
 
 
 @router.post("/debt-target", response_class=HTMLResponse)

src/quartermaster/routes_month.py

@@ -70,6 +70,24 @@ def _render_target(request: Request, db: Session, month: Month) -> HTMLResponse:
     )
 
 
+def _render_zero(request: Request, month: Month) -> HTMLResponse:
+    zero = month_service.month_zero(month)
+    return templates.TemplateResponse(
+        request,
+        "partials/month_zero.html",
+        {
+            "zero": zero,
+            "planned_tone": service.zero_tone(zero.planned),
+            "applied_tone": service.zero_tone(zero.applied),
+        },
+    )
+
+
+def _append_oob(base: HTMLResponse, *extras: HTMLResponse) -> HTMLResponse:
+    body = base.body.decode() + "".join(e.body.decode() for e in extras)
+    return HTMLResponse(body)
+
+
 @router.get("", response_class=HTMLResponse)
 def view_month(
     year_month: str,
@@ -92,6 +110,7 @@ def view_month(
                 "all_months": all_months,
             },
         )
+    zero = month_service.month_zero(month)
     return templates.TemplateResponse(
         request,
         "month.html",
@@ -107,6 +126,9 @@ def view_month(
                 (e for e in month.entries if e.section == Section.debt_minimum),
                 key=lambda e: e.id,
             ),
+            "zero": zero,
+            "planned_tone": service.zero_tone(zero.planned),
+            "applied_tone": service.zero_tone(zero.applied),
         },
     )
 
@@ -144,7 +166,10 @@ def add_month_entry(
         db, month, section, clean_name, _parse_amount(planned)
     )
     db.refresh(month)
-    return _render_section(request, month, section)
+    return _append_oob(
+        _render_section(request, month, section),
+        _render_zero(request, month),
+    )
 
 
 @router.delete("/entries/{entry_id}", response_class=HTMLResponse)
@@ -159,11 +184,10 @@ def delete_month_entry(
     if section is None:
         raise HTTPException(status_code=404, detail="entry not found")
     db.refresh(month)
-    response = _render_section(request, month, section)
+    extras: list[HTMLResponse] = [_render_zero(request, month)]
     if section == Section.debt_minimum:
-        target_html = _render_target(request, db, month).body.decode()
-        response = HTMLResponse(response.body.decode() + target_html)
-    return response
+        extras.append(_render_target(request, db, month))
+    return _append_oob(_render_section(request, month, section), *extras)
 
 
 @router.post("/entries/{entry_id}", response_class=HTMLResponse)
@@ -195,7 +219,10 @@ def update_month_entry(
     if updated is None:
         raise HTTPException(status_code=404, detail="entry not found")
     db.refresh(month)
-    return _render_section(request, month, updated.section)
+    return _append_oob(
+        _render_section(request, month, updated.section),
+        _render_zero(request, month),
+    )
 
 
 @router.post("/target", response_class=HTMLResponse)

src/quartermaster/static/app.css

@@ -157,6 +157,59 @@ button[type=submit] {
   border-bottom-style: dashed;
 }
 
+/* Zero Amount widget ----------------------------------------------------- */
+
+:root {
+  --tone-zero: #2f6b4f;
+  --tone-positive: #b77b00;
+  --tone-negative: #a03030;
+}
+
+.zero-widget {
+  margin-top: 1rem;
+  padding: 1rem 1.25rem;
+  background: #fff;
+  border: 1px solid var(--rule);
+  border-radius: 6px;
+  text-align: center;
+}
+
+.zero-widget .zero-label {
+  font-size: 0.75rem;
+  text-transform: uppercase;
+  letter-spacing: 0.15em;
+  color: var(--muted);
+  margin-bottom: 0.25rem;
+}
+
+.zero-widget .zero-value {
+  font-size: 2.4rem;
+  font-weight: 700;
+  font-variant-numeric: tabular-nums;
+  line-height: 1.1;
+}
+
+.zero-widget .zero-sublabel {
+  font-size: 0.7rem;
+  text-transform: uppercase;
+  letter-spacing: 0.1em;
+  color: var(--muted);
+}
+
+.zero-widget-pair .zero-values {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 1.5rem;
+}
+
+.zero-widget-pair .zero-value {
+  font-size: 2rem;
+}
+
+.tone-zero { color: var(--tone-zero); }
+.tone-positive { color: var(--tone-positive); }
+.tone-negative { color: var(--tone-negative); }
+
 /* Monthly view ----------------------------------------------------------- */
 
 .month-nav {

src/quartermaster/templates/index.html

@@ -18,6 +18,7 @@
       </select>
     {% endif %}
   </nav>
+  {% include "partials/budget_zero.html" %}
   {% for section in sections %}
     {% if section.section.value == 'debt_minimum' %}
       {% include "partials/section.html" %}

src/quartermaster/templates/month.html

@@ -2,6 +2,7 @@
 {% block content %}
 <div class="budget">
   {% include "partials/month_nav.html" %}
+  {% include "partials/month_zero.html" %}
   {% for section in sections %}
     {% if section.section.value == 'debt_minimum' %}
       {% include "partials/month_section.html" %}

src/quartermaster/templates/partials/budget_zero.html

@@ -0,0 +1,4 @@
+<section class="zero-widget" id="zero-widget" hx-swap-oob="outerHTML">
+  <div class="zero-label">Zero Amount</div>
+  <div class="zero-value tone-{{ tone }}">${{ '%.2f' | format(zero) }}</div>
+</section>

src/quartermaster/templates/partials/month_zero.html

@@ -0,0 +1,13 @@
+<section class="zero-widget zero-widget-pair" id="zero-widget" hx-swap-oob="outerHTML">
+  <div class="zero-label">Zero Amount</div>
+  <div class="zero-values">
+    <div class="zero-cell">
+      <div class="zero-sublabel">Planned</div>
+      <div class="zero-value tone-{{ planned_tone }}">${{ '%.2f' | format(zero.planned) }}</div>
+    </div>
+    <div class="zero-cell">
+      <div class="zero-sublabel">Applied</div>
+      <div class="zero-value tone-{{ applied_tone }}">${{ '%.2f' | format(zero.applied) }}</div>
+    </div>
+  </div>
+</section>