docs: update validator page with PIP-49 delegation fields

- Fix 'Last Joined Height' to 'Last Sortition Height' per source code
- Add optional delegation fields from PIP-49 (DelegateOwner, DelegateShare, DelegateExpiry)
- Update structure size: 120 bytes base, 153 bytes with delegation

Author: b00f

content/protocol/blockchain/validator.md

@@ -10,21 +10,38 @@ The amount of stake held by validators determines their power in the consensus.
 
 ## Validator Structure
 
-The Validator structure is 120 bytes long and consists of the following fields:
+The base Validator structure is 120 bytes long and consists of the following fields:
 
-| Field               | Size     |
-| ------------------- | -------- |
-| Public Key          | 96 bytes |
-| Number              | 4 bytes  |
-| Stake               | 8 bytes  |
-| Last Bonding Height | 4 bytes  |
-| Unbonding Height    | 4 bytes  |
-| Last Joined Height  | 4 bytes  |
+| Field                | Size     |
+| -------------------- | -------- |
+| Public Key           | 96 bytes |
+| Number               | 4 bytes  |
+| Stake                | 8 bytes  |
+| Last Bonding Height  | 4 bytes  |
+| Unbonding Height     | 4 bytes  |
+| Last Sortition Height| 4 bytes  |
 
 - **Public Key** is the Validator's public key.
 - **Number** is a sequential and unique number assigned to each validator when it is created for the first time.
   The validator number is used to calculate the [state hash](/protocol/blockchain/state-hash) of the blockchain.
 - **Stake** holds the Validator's stake or the amount of Pactus coins locked or "staked" by the Validator.
-- **Bonding Height** is the last block height that the validator has bonded their stake.
-- **Unbonding Height** is the block height that the validator's stake is unbonded.
-- **Last Joined Height** is the block height that the validator joined the committee.
+- **Last Bonding Height** is the last block height at which the validator bonded stake.
+- **Unbonding Height** is the block height at which the validator's stake is unbonded.
+  If greater than zero, the validator is considered unbonded.
+- **Last Sortition Height** is the last block height at which the validator evaluated sortition.
+
+## Delegation (PIP-49)
+
+[PIP-49](https://pips.pactus.org/PIPs/pip-49) introduces an optional delegation section that adds 33 bytes to the structure:
+
+| Field           | Size     |
+| --------------- | -------- |
+| Delegate Owner  | 21 bytes |
+| Delegate Share  | 8 bytes  |
+| Delegate Expiry | 4 bytes  |
+
+When the delegation fields are present, the total structure size is 153 bytes. If the delegation section is absent, the validator is not delegated.
+
+- **Delegate Owner** is the address of the stake owner account.
+- **Delegate Share** is the stake owner's reward share in nano PAC (within `[0, 0.7 PAC]`).
+- **Delegate Expiry** is the block height at which the delegation expires (zero means no expiry).