Add defi/vault-strategy: manager-run investment vault with Pyth oracle and rebalancing

Adds a new example under defi/vault-strategy/anchor demonstrating a
manager-custodial investment vault on Solana.

## What this adds

### vault-strategy program
- `initialize_strategy` — creates the Strategy PDA, share mint, and vault
  ATAs for USDC/TSLAx/NVDAx; registers Pyth price feed pubkeys
- `deposit` — accepts USDC, prices shares against Pyth-computed NAV,
  mints proportional LP shares to the depositor
- `invest` — manager-only CPI to the swap router to convert USDC into
  basket tokens (TSLAx or NVDAx)
- `rebalance` — manager-only atomic two-leg CPI: sell one basket token
  for USDC then buy the other, with slippage protection on both legs
- `collect_fees` — permissionless; accrues the annual management fee by
  minting new shares to the manager (dilution model)
- `withdraw` — burns shares, returns proportional in-kind slice of every
  vault asset (USDC + TSLAx + NVDAx) to the user

### mock-swap-router program (test fixture)
- Stores per-asset `usdc_per_token` exchange rates in `AssetRate` PDAs
- `swap_usdc_for_asset` — receives USDC, mints basket tokens (used by invest)
- `swap_asset_for_usdc` — burns basket tokens, releases USDC (used by rebalance)
- `router_authority` PDA holds mint authority for all basket token mints

### Oracle (Pyth)
NAV is computed from Pyth `PriceUpdateV2` accounts. Feed pubkeys are
stored in the Strategy at creation. Prices older than 60 seconds are
rejected. Raw byte offsets are used to read price data, avoiding the
borsh 0.10/1.x incompatibility between the Pyth SDK and Anchor 1.0.

### Financial math
No floats; u128 intermediates; multiply-before-divide; all arithmetic
via checked_* methods; transfer_checked for all token moves.

### Tests (LiteSVM, 8 tests)
Covers all instructions including NAV-based deposit pricing, fee accrual
via mock clock advancement, in-kind withdrawal, rebalance, and slippage
rejection. Mock Pyth PriceUpdateV2 accounts injected directly into LiteSVM.

### Also adds
- defi/ workspace members in root Cargo.toml
- Vault Strategy entry in root README.md

https://claude.ai/code/session_01XUvydGu8rPSbM1AxLJ2GpA

Author: claude

Cargo.lock

@@ -48,6 +48,10 @@ members = [
     "basics/transfer-sol/anchor/programs/*",
     "basics/transfer-sol/asm",
 
+    # defi
+    "defi/vault-strategy/anchor/programs/vault-strategy",
+    "defi/vault-strategy/anchor/programs/mock-swap-router",
+
     # tokens
     "tokens/token-extensions/mint-close-authority/native/program",
     "tokens/token-extensions/non-transferable/native/program",

Cargo.toml

@@ -41,6 +41,12 @@ Read offchain price data [onchain](https://solana.com/docs/terminology#onchain)
 
 [⚓ Anchor](./oracles/pyth/anchor) [💫 Quasar](./oracles/pyth/quasar)
 
+### Vault Strategy
+
+Manager-run investment vault — deposit USDC, manager allocates across a basket of assets (TSLAx, NVDAx), withdraw proportional in-kind assets. Demonstrates share minting, NAV-based pricing, management fee accrual, and CPI to a swap router.
+
+[⚓ Anchor](./defi/vault-strategy/anchor)
+
 ## Basics
 
 ### Hello Solana

README.md

@@ -0,0 +1,6 @@
+.anchor
+.DS_Store
+target
+**/*.rs.bk
+node_modules
+test-ledger

defi/vault-strategy/anchor/.gitignore

@@ -0,0 +1,17 @@
+[toolchain]
+solana_version = "3.1.8"
+
+[features]
+resolution = true
+skip-lint = false
+
+[programs.localnet]
+vault_strategy = "VLT5W7bqhRN4nCdRpXm8UfHRxZd9EuZGqiSAkGHQfGh"
+mock_swap_router = "SWPR8Rk3aq3DrDGLdaANq7xCMnXoUFUJWJJmCWxc8Jm"
+
+[provider]
+cluster = "Localnet"
+wallet = "~/.config/solana/id.json"
+
+[scripts]
+test = "cargo test"

defi/vault-strategy/anchor/Anchor.toml

@@ -0,0 +1,15 @@
+[workspace]
+members = [
+    "programs/*"
+]
+resolver = "2"
+
+[profile.release]
+overflow-checks = true
+lto = "fat"
+codegen-units = 1
+
+[profile.release.build-override]
+opt-level = 3
+incremental = false
+codegen-units = 1