Add 'Why Update Prices' section to EVM Pull Integration guide (#908)

* Add callout explaining why price updates are needed in Pull integration

- Added a warning callout before the 'Write Contract Code' section
- Explains the pull-based oracle model concept
- Highlights advantages: lower costs, lower latency, flexibility
- Details the three steps required in Pull integration
- Warns about StalePrice error when prices aren't updated

Co-Authored-By: Nidhi Singh <[email protected]>

* Fix formatting (prettier and trailing whitespace)

Co-Authored-By: Nidhi Singh <[email protected]>

* Move title inside callout per review feedback

Co-Authored-By: Nidhi Singh <[email protected]>

* Restructure to have section heading with Important note in callout

Per feedback from @nidhi-singh02:
- Added 'Why Update Prices' as a section heading
- Moved explanatory content outside the callout
- Kept only the Important note about StalePrice errors in the callout

Co-Authored-By: Nidhi Singh <[email protected]>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Nidhi Singh <[email protected]>

Author: devin-ai-integration[bot]

pages/price-feeds/use-real-time-data/pull-integration/evm.mdx

@@ -46,6 +46,29 @@ Then add the following line to your `remappings.txt` file:
 @pythnetwork/pyth-sdk-solidity/=node_modules/@pythnetwork/pyth-sdk-solidity
 ```
 
+## Why Update Prices
+
+Pyth uses a pull-based oracle model. Unlike traditional push oracles that automatically update prices on-chain at regular intervals, Pyth requires users to explicitly update the on-chain price before reading it.
+
+This design offers several advantages:
+
+- **Lower costs**: You only pay for price updates when you need them
+- **Lower latency**: You can fetch the latest price update directly from Pyth's low-latency oracle network and submit it on-chain immediately
+- **Flexibility**: Different applications can update prices at different frequencies based on their needs
+
+In the Pull integration pattern, your contract must:
+
+1. Accept `priceUpdate` data from the caller (fetched from [Hermes](../../how-pyth-works/hermes))
+2. Call `updatePriceFeeds()` to submit this data on-chain before reading prices
+3. Pay a small fee for each update (calculated via `getUpdateFee()`)
+
+<Callout type="warning" emoji="⚠️">
+  **Important**: If you don't update the price or if the on-chain price becomes
+  too stale, calls to `getPriceNoOlderThan()` will revert with a `StalePrice`
+  error (0x19abf40e). See [how to fetch price
+  updates](../../fetch-price-updates) for more details.
+</Callout>
+
 ## Write Contract Code
 
 The code snippet below provides a general template for what your contract code should look like: