feat: add finance module (TVM + bonds) [3.1.0]

Phase 1 of multi-phase expansion. Adds Excel-compatible TVM
functions and bond analytics with full test coverage.

- TVM: fv, pv, pmt, nper, ipmt, ppmt, rate, npv, irr, mirr,
  cagr, compoundInterest, discountFactor, amortizationSchedule
- Bonds: cleanPrice, dirtyPrice, accruedInterest,
  yieldToMaturity, macaulay/modified duration, convexity,
  dv01, priceChangeApprox
- 24 new tests (90 total passing)
- docs/FINANCE.md
- Cleanup: drop test-install/, pnpm-lock.yaml
- Ship CHANGELOG.md to npm bundle

Author: MeridianAlgo-Developer

.gitignore

@@ -67,3 +67,4 @@ docs/.vitepress/dist/
 
 # Release files
 release-instructions.md
+.claude-memory/

CHANGELOG.md

@@ -5,6 +5,22 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.1.0] - 2026-05-02
+
+### Added
+- **Finance module (`src/finance/`)** with TVM and bond analytics.
+- **TVM functions** (Excel-compatible): `fv`, `pv`, `pmt`, `nper`, `ipmt`, `ppmt`, `rate`, `npv`, `irr`, `mirr`, `cagr`, `compoundInterest`, `discountFactor`, `amortizationSchedule`.
+- **Bond pricing**: `cleanPrice`, `dirtyPrice`, `accruedInterest`, `yieldToMaturity`, `macaulayDuration`, `modifiedDuration`, `convexity`, `dv01`, `priceChangeApprox`.
+- 24 new tests (90 total passing).
+- `docs/FINANCE.md` reference.
+
+### Removed
+- Stale `test-install/` directory.
+- Duplicate `pnpm-lock.yaml` (kept `package-lock.json`).
+
+### Notes
+This is **Phase 1** of a multi-phase expansion. Subsequent minor releases will add: Black-Scholes + stochastic models (3.2), yield curves + credit (3.3), risk/vol upgrade (3.4), execution algos + microstructure (3.5), HRP/Kelly/factor models (3.6), candlestick patterns + advanced indicators (3.7), ML + regime detection (3.8), Deno/Bun/UMD targets (3.9).
+
 ## [3.0.0] - 2026-04-21
 
 ### Added

docs/FINANCE.md

@@ -0,0 +1,98 @@
+# Finance Module
+
+Time Value of Money (TVM) and Bond analytics. Spreadsheet-compatible signatures (Excel/Google Sheets parity).
+
+## Sign Convention
+
+Cash inflows positive, outflows negative. Matches Excel.
+
+## TVM Functions
+
+```ts
+import {
+  fv, pv, pmt, nper, ipmt, ppmt, rate,
+  npv, irr, mirr,
+  cagr, compoundInterest, discountFactor,
+  amortizationSchedule,
+} from 'meridianalgo';
+```
+
+### Core
+
+| Function | Purpose |
+|----------|---------|
+| `fv(rate, nper, pmt?, pv?, when?)` | Future value |
+| `pv(rate, nper, pmt?, fv?, when?)` | Present value |
+| `pmt(rate, nper, pv, fv?, when?)` | Periodic payment |
+| `nper(rate, pmt, pv, fv?, when?)` | Number of periods |
+| `ipmt(rate, per, nper, pv, fv?, when?)` | Interest portion of period payment |
+| `ppmt(rate, per, nper, pv, fv?, when?)` | Principal portion |
+| `rate(nper, pmt, pv, fv?, when?, guess?)` | Solve interest rate (Newton-Raphson) |
+
+`when`: `0` = end of period (default), `1` = beginning (annuity due).
+
+### Cash Flow Analysis
+
+| Function | Purpose |
+|----------|---------|
+| `npv(rate, cashflows[])` | Net Present Value (cf[0] at t=0) |
+| `irr(cashflows[], guess?)` | Internal Rate of Return |
+| `mirr(cashflows[], financeRate, reinvestRate)` | Modified IRR |
+
+### Helpers
+
+- `cagr(begin, end, years)` — Compound Annual Growth Rate
+- `compoundInterest(principal, rate, periods, compoundsPerPeriod?)`
+- `discountFactor(rate, t)`
+- `amortizationSchedule(principal, ratePerPeriod, nper, when?)` — full per-period schedule
+
+### Examples
+
+```ts
+// 30-year mortgage, $200k @ 6%
+const monthlyPayment = pmt(0.06 / 12, 360, 200000);
+// → -1199.10
+
+// Project IRR
+const r = irr([-1000, 300, 400, 500, 600]);
+// → ~0.1487
+
+// 7-year CAGR
+cagr(1000, 2000, 7);
+// → 0.10409
+```
+
+## Bonds
+
+```ts
+import {
+  cleanPrice, dirtyPrice, accruedInterest, yieldToMaturity,
+  macaulayDuration, modifiedDuration, convexity, dv01,
+  priceChangeApprox,
+} from 'meridianalgo';
+```
+
+`BondParams = { face, couponRate, ytm, yearsToMaturity, frequency? }` — frequency defaults to 2 (semi-annual).
+
+| Function | Returns |
+|----------|---------|
+| `cleanPrice(params)` | Flat price |
+| `dirtyPrice(params, daysSinceLastCoupon, daysInPeriod)` | Invoice price (clean + AI) |
+| `accruedInterest(face, couponRate, freq, daysSince, daysInPeriod)` | Accrued coupon |
+| `yieldToMaturity(price, face, couponRate, years, freq?)` | YTM (bisection) |
+| `macaulayDuration(params)` | Macaulay duration (years) |
+| `modifiedDuration(params)` | Modified duration |
+| `convexity(params)` | Convexity |
+| `dv01(params)` | Price value of 1 bp |
+| `priceChangeApprox(params, dy)` | Δprice from duration + convexity |
+
+### Example
+
+```ts
+const bond = { face: 1000, couponRate: 0.05, ytm: 0.06, yearsToMaturity: 10, frequency: 2 };
+const price = cleanPrice(bond);             // 925.61
+const ytm = yieldToMaturity(price, 1000, 0.05, 10, 2); // 0.06
+const mod = modifiedDuration(bond);         // ~7.66
+const conv = convexity(bond);               // ~74
+const bp1 = dv01(bond);                     // ~0.71
+```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "meridianalgo",
-  "version": "3.0.0",
+  "version": "3.1.0",
   "description": "Professional-grade quantitative finance framework for JavaScript/TypeScript - algorithmic trading, backtesting, risk management, and portfolio optimization",
   "main": "dist/index.js",
   "module": "dist/index.mjs",
@@ -83,7 +83,8 @@
   "files": [
     "dist",
     "README.md",
-    "LICENSE"
+    "LICENSE",
+    "CHANGELOG.md"
   ],
   "directories": {
     "doc": "docs",