feat(twap-oracle): implement CreateCurrentTickAccount and UpdateCurrentTick

Add CurrentTickAccount — an oracle-owned PDA (one per price source) that holds
the latest raw tick written by the price source and a timestamp. The price source
calls UpdateCurrentTick after each price-changing operation; anyone can then call
RecordTick (upcoming) to advance the PriceObservations accumulator without
requiring the price source to be present. PDA is derived from price_source_id
only (no window) since a single current tick serves all time windows.

Add price_to_tick(price: u128) -> i32 to twap_oracle_core: isqrt(price << 128)
-> sqrtPriceX96 -> get_tick_at_sqrt_ratio. The sqrtPriceX96 is clamped to
>= MIN_SQRT_RATIO so a zero/dust price maps to MIN_TICK rather than erroring.

Add a pure-integer integer_sqrt(U256) (bit-by-bit, no floating point): ruint's
root is gated behind its std feature and seeds with f64, neither available in
the guest. Uses wrapping_shr for the digit loop (checked_shr rejects the
intended lossy shifts).

Pull in uniswap_v3_math (for get_tick_at_sqrt_ratio) and alloy-primitives
(U256), with ruint pinned to =1.17.0 — 1.18 raised its MSRV to rustc 1.90,
above the risc0 guest toolchain's 1.88.

programs/twap_oracle/methods/guest/src/bin/twap_oracle.rs

@@ -77,4 +77,57 @@ mod twap_oracle {
             );
         Ok(spel_framework::SpelOutput::execute(post_states, vec![]))
     }
+
+    /// Creates and initialises a current tick account for a price source.
+    ///
+    /// Expected accounts:
+    /// 1. `current_tick_account` — uninitialized PDA owned by this oracle program.
+    /// 2. `price_source` — account the caller controls (proven via `is_authorized = true`).
+    /// 3. `clock` — read-only LEZ clock account.
+    ///
+    /// `initial_price` is a `Q64.64` spot price; the oracle converts it to a tick.
+    #[instruction]
+    pub fn create_current_tick_account(
+        ctx: ProgramContext,
+        current_tick_account: AccountWithMetadata,
+        price_source: AccountWithMetadata,
+        clock: AccountWithMetadata,
+        initial_price: u128,
+    ) -> SpelResult {
+        let post_states =
+            twap_oracle_program::create_current_tick_account::create_current_tick_account(
+                current_tick_account,
+                price_source,
+                clock,
+                initial_price,
+                ctx.self_program_id,
+            );
+        Ok(spel_framework::SpelOutput::execute(post_states, vec![]))
+    }
+
+    /// Updates the tick stored in an existing current tick account.
+    ///
+    /// Expected accounts:
+    /// 1. `current_tick_account` — initialized PDA owned by this oracle program.
+    /// 2. `price_source` — account the caller controls (proven via `is_authorized = true`).
+    /// 3. `clock` — read-only LEZ clock account.
+    ///
+    /// `price` is a `Q64.64` spot price; the oracle converts it to a tick.
+    #[instruction]
+    pub fn update_current_tick(
+        ctx: ProgramContext,
+        current_tick_account: AccountWithMetadata,
+        price_source: AccountWithMetadata,
+        clock: AccountWithMetadata,
+        price: u128,
+    ) -> SpelResult {
+        let post_states = twap_oracle_program::update_current_tick::update_current_tick(
+            current_tick_account,
+            price_source,
+            clock,
+            price,
+            ctx.self_program_id,
+        );
+        Ok(spel_framework::SpelOutput::execute(post_states, vec![]))
+    }
 }