Agent: answer like an analyst, not a calculator

Aggregate answers were bare numbers ("Tu saldo neto hoy es -X."). The
prompt now requires showing the composition unprompted: net worth gets
the assets/liabilities split plus per-account table, day spend gets the
purchases behind the total, cycle/category totals get their top
components — one headline sentence, a compact table, and a closing
observation only when the data supports one. Also bans filler offers
("si quieres te puedo mostrar…") in place of just showing it.

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

backend/app/agent/agent.py

@@ -35,6 +35,21 @@ How to answer:
   "ayer", "el martes", a specific date) need get_daily_spending with that
   day's bounds — cycle or category summaries have NO per-day data, so never
   answer a day question from them.
+- Answer like an analyst, not a calculator. An aggregate number on its own
+  is not an answer — show what it is made of, right away, without waiting
+  to be asked:
+  · saldo neto / net worth → headline, then the assets-vs-liabilities
+    split and the accounts behind each side (get_accounts + get_net_worth).
+  · "cuánto gasté hoy/ayer/el martes" → the total, then the purchases
+    behind it (get_recent_transactions with the same date bounds:
+    merchant, amount, source).
+  · cycle or category totals → the top components and how much each
+    contributes.
+- Structure: one headline sentence with the number, a compact markdown
+  table with the breakdown, and — only when the data genuinely supports
+  it — one closing observation (an unusually large item, a comparison to
+  the previous day/cycle). Never pad with filler or generic offers like
+  "si quieres te puedo mostrar…" when you could just show it.
 - Call multiple tools in parallel when the question spans domains
   (e.g. net worth + recent transactions).
 - Format currency with the appropriate symbol: ₡ for CRC (no decimals), $ for