docs: monthly expense baseline and emergency reserve analysis

One-off analysis, nothing built. Realistic baseline $4,140/mo -> $24,800 for
six months, against $89,770 already accessible ($81,017 loan redraw + $8,753
offset).

Records four corrections the raw data needs before any restatement:
misfiled Raiz/Vanguard/moomoo debits counted as spend, `other` credits read as
negative spend, `government` conflating ATO with rates/rego, and `fees` being
mostly annual.

CLAUDE.md gains two traps found while doing it: partial split coverage inside a
category is usually correct rather than a gap (only shared utilities and
subscriptions are split), and the loan repayment is voluntarily above contracted
($2,500 vs $1,190.54 per fortnight) with the difference recoverable via redraw.

CLAUDE.md

@@ -135,6 +135,19 @@ populated on only one. And Sonu's loan contributions (`…emi` in the offset
 account, 39 rows, $37,980.24) are categorised `transfers`, indistinguishable from
 ordinary internal transfers.
 
+**Partial split coverage inside a category is usually correct, not a gap.** Only
+*shared* items are split. `utilities` sits at 69% yours because Globird, OVO, GWW
+and home telecoms are split while Telstra, Vodafone, Optus and JB Hi-Fi Mobile
+are personal. `subscriptions` is 91% because Uber One, Amazon Prime and OnePass
+are shared while Claude, OpenAI, Anthropic, OpenRouter, You.com, LinkedIn, Xero,
+Billdu, Spotify and Patreon are not. `fees` and `charity` are 100% yours and
+correct. Check the merchants before concluding a rule was never applied — a
+category-level ratio that "looks wrong" usually is not.
+
+Splits exist in this app from **2026-01-09** only; earlier splits lived in
+SplitMyExpenses. So a trailing-12-month per-person series splices six months of
+gross onto six months of net. Use Feb–Jun 2026 for anything per-person.
+
 ### The shared loan
 
 The loan is a **separate ledger**, not a shared expense and not a settlement
@@ -152,6 +165,19 @@ months $63,500 of cash left and debt fell $44,127.36, and the $16,523.64
 difference bought nothing. Excluding it would leave the balance sheet unable to
 reconcile cash out against equity gained.
 
+**The repayment is voluntarily above contracted, and the gap is the largest
+flexible cost in the whole picture.** Contracted is $1,190.54/fortnight
+($2,579.50/mo annualised); the actual direct debit is $2,500.00/fortnight
+($5,416.67/mo). That is $2,837.17/mo of overpayment, and it is *not* sunk — it
+shows up as `statements.redraw_available`, which grew $62,387.17 → $81,017.42
+across the two most recent loan statements. Sonu returned to $1,250/fortnight in
+July 2026 after the reduced $750 period during her leave.
+
+Treat the repayment as two figures whenever asking "what does this cost me":
+the contracted floor and the actual. `scheduled_repayment` holds the actual
+($2,500), not the contracted minimum — the contracted figure is not in the DB at
+all. See `docs/expense-baseline.md`.
+
 ### Import Date (`created_at`)
 
 `transactions.created_at` is the import timestamp (DB default `now()`). In the transactions and shared views, the "Imported" column shows:
@@ -349,6 +375,11 @@ See `README.md` → **Known Gaps / TODOs** for full details.
 - **Shared expenses redesign** — `docs/shared-expenses-design.md`. Phase 0 done;
   Phases 1–4 unbuilt. Deliberately paused to live with the current behaviour
   before committing to a model designed in one session.
+- **Expense baseline / emergency reserve** — `docs/expense-baseline.md`. One-off
+  analysis, nothing built. Records four data corrections the raw numbers need
+  (misfiled Raiz/super/brokerage debits, `other` credits read as negative spend,
+  `government` conflating ATO with rates/rego, `fees` being mostly annual) and
+  why only Feb–Jun 2026 is trustworthy for per-person figures.
 - **11 statements fail the balance assertion**, ~$4,177 unexplained. Predates
   this work. One ANZ statement is off by exactly $0.50, traced to a misread digit
   in fee rows ($5.00 vs $5.50).