Add Extensions and C-Token documentation

.gitignore

@@ -2,3 +2,5 @@ mintlify
 mintlify-docs/
 /CLAUDE.md
 .windsurf.context/
+.claude
+.context

compressed-token-program/Extensions/compressible.mdx

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+---
+title: Compressible
+description: The compressible extension sponsors rent-exemption for any type of Solana account except mints. 
+---
+
+<table>
+  <thead>
+    <tr>
+      <th style={{width: '20%', textAlign: 'left'}}></th>
+      <th style={{width: '20%', textAlign: 'left'}}>Supported Accounts</th>
+      <th style={{width: '45%', textAlign: 'left'}}>Description</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td style={{textAlign: 'left'}}>**Compressible**</td>
+      <td style={{textAlign: 'left'}}>
+        cToken accounts
+      </td>
+      <td style={{textAlign: 'left'}}>
+        * **Sponsored rent-exemption**
+        * 200x cheaper than SPL tokens
+        * Must be **added at account creation**
+      </td>
+    </tr>
+  </tbody>
+</table>
+
+## Key Points
+Compressible accounts maintain the **functionality of Solana accounts** but with **rent-exemption sponsorship**: 
+
+1. The protocol funds the account's rent exemption (rent sponsor) at creation.
+2. The account creator top-ups the lamport balance with rent for at least two epochs (12,600 slots / 84 min)
+3. The transaction payer top-ups the lamports balance with transactions that write to compressible accounts to keep the account decompressed.
+4. The account will be compressed when inactive for a period of 12,600 slots (84 min).
+5. When the account is written to, it's automatically decompressed.
+
+### Cost Comparison 
+This extension makes cToken accounts 200x cheaper than SPL token accounts
+
+    |  | cToken | SPL |
+    |-----------|--------|-----|
+    | allocate | 0.000011 | 0.002 |
+    | rent for 24h | 0.000005 | - |
+
+<Accordion title="Core Concepts: Solana Rent vs Compressible Accounts">
+
+The **creator of Solana accounts** pays the **rent exemption balance equal to 2 years of rent**.
+The rent-exempt balance is proportional to account size (calculated in lamports):
+
+``` rust
+minimum_balance = (ACCOUNT_STORAGE_OVERHEAD + data_len) * lamports_per_byte * exemption_threshold
+
+/// Example 100 byte account:
+/// minimum_balance = (128 + 100) * 6960 = 1,586,880 lamports
+```
+<Note>
+* Most Solana accounts are rarely accessed after creation, but continue to lock up SOL for the account's lifetime.
+* The creator still must pay the rent-exemption balance.
+</Note>
+
+**Compressible accounts** build on top of Solana's rent system, but use epochs with a length of 6300 slots to calculate rent.
+The **creator pays** the account with **rent for at least two epochs**:
+
+``` rust
+rent_per_epoch = base_rent + (data_len * lamports_per_byte_per_epoch)
+/// Example 100 byte account:  128 + (100 * 1) = 228 rent per epoch
+```
+
+</Accordion>
+
+## Create a cToken Account with Compressible Extension
+
+Here are the steps to create a compressible account:
+
+1. **Set the initial lamports balance** to N epochs (must be at least 2 epochs)
+   * Customize N **based on expected account activity**.
+   * The account stays decompressed for N epochs.
+
+   * Paid by the **account creator**.
+2. **Set the top-up amount** for writes when the account balance falls below the set lamports balance.
+   * Determines how much lamports are added when the account needs a top-up.
+   * Top-ups are made by the **transaction fee payer** when the account is written to and is below the set lamports balance.
+
+<Note>
+* Accounts become compressible when they advance two epochs without new transactions that add lamports.
+* A forester node compresses the account after these two epochs and the protocol can reclaim the rent.
+</Note>
+
+```rust 
+use light_token_client::actions::{
+    create_compressible_token_account,
+    CreateCompressibleTokenAccountInputs,
+};
+use light_ctoken_types::state::TokenDataVersion;
+
+let token_account_pubkey = create_compressible_token_account(
+    &mut rpc,
+    CreateCompressibleTokenAccountInputs {
+        owner: owner_pubkey,
+        mint: mint_pubkey,
+        payer: &payer_keypair,
+        num_prepaid_epochs: 10,  // 0 or ≥2
+        lamports_per_write: Some(5_000), // lamports added per top-up
+        token_account_version: TokenDataVersion::ShaFlat,
+        token_account_keypair: None,  // SDK generates keypair
+    }
+).await?;
+```
+
+<Note>
+For associated cToken accounts derive the address with [owner, compressed_token_program_id, mint](https://solscan.io/account/cTokenmWW8bLPjZEBAUgYy3zKxQZW6VKi7bqNFEVv3m).
+</Note>
+
+### Creation Cost
+
+Creating a compressible cToken account (260 bytes) incurs these costs:
+
+<table>
+  <thead>
+    <tr>
+      <th style={{width: '25%', textAlign: 'left'}}>Component</th>
+      <th style={{width: '25%', textAlign: 'left'}}>Amount</th>
+      <th style={{width: '23%', textAlign: 'left'}}>Paid By</th>
+      <th style={{width: '27%', textAlign: 'left'}}>Description</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>Solana rent exemption</td>
+      <td>~2,700,480 lamports</td>
+      <td>Rent sponsor PDA</td>
+      <td>Rent-exemption balance</td>
+    </tr>
+    <tr>
+      <td>Prepaid rent</td>
+      <td>388 × N epochs*</td>
+      <td>Payer <br />(Account creator)</td>
+      <td>Rent for N epochs</td>
+    </tr>
+    <tr>
+      <td>Compression incentive</td>
+      <td>10,000 lamports <br /> + 1,000 lamports</td>
+      <td>Payer <br />(Account creator)</td>
+      <td>Base compression cost<br />+ protocol incentive</td>
+    </tr>
+    <tr>
+      <td>Transaction fee</td>
+      <td>5,000-10,000 lamports</td>
+      <td>Payer <br />(Account creator)</td>
+      <td>Standard Solana tx fees</td>
+    </tr>
+  </tbody>
+</table>
+
+\* `N` = `num_prepaid_epochs` parameter (0 or 2+, set at creation).
+
+### Top-ups per Transaction
+
+When creating a compressible account, you can configure `lamports_per_write` to automatically add rent on each write ("Top-Up").
+This keeps accounts decompressed while active.
+
+The payer's cost depends on the account's funding state:
+
+<table>
+  <thead>
+    <tr>
+      <th style={{width: '30%', textAlign: 'left'}}>Account State</th>
+      <th style={{width: '25%', textAlign: 'left'}}>Payer Cost</th>
+      <th style={{width: '45%', textAlign: 'left'}}>Example</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>Funded for 2+ epochs</td>
+      <td>0 lamports</td>
+      <td>No top-up required</td>
+    </tr>
+    <tr>
+      <td>Funded for less than 2 epochs</td>
+      <td>`lamports_per_write`</td>
+      <td>Configured as 5,000 lamports <br />→ payer pays 5,000 lamports</td>
+    </tr>
+    <tr>
+      <td>Compressible<br />(ran out of rent)</td>
+      <td>`lamports_per_write + rent_deficit`</td>
+      <td>Configured top-up: 5,000 lamports<br />Rent deficit: 3,000 lamports<br />Total payer cost: 8,000 lamports</td>
+    </tr>
+  </tbody>
+</table>
+
+<Note>
+Top-ups are additional to standard Solana transaction fees (typically &lt;10,000 lamports).
+</Note>
+
+### Closing compressible accounts
+
+Compressible accounts can be closed by two parties. How rent and lamports balance are distributed depends on which party closes the account.
+
+1. The **Account Owner** can close the account at any time, regardless of rent status. The account is not compressed in this case.
+
+<table>
+  <thead>
+    <tr>
+      <th style={{width: '35%', textAlign: 'left'}}>Component and Amount</th>
+      <th style={{width: '35%', textAlign: 'left'}}>Recipient</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>Rent exemption + completed epoch rent</td>
+      <td>Rent sponsor</td>
+    </tr>
+    <tr>
+      <td>Remaining lamports from top-up (partial epoch)</td>
+      <td>Account Owner</td>
+    </tr>
+  </tbody>
+</table>
+
+2. The **Compression Authority** can compress and close the account when it becomes compressible
+
+<table>
+  <thead>
+    <tr>
+      <th style={{width: '35%', textAlign: 'left'}}>Component and Amount</th>
+      <th style={{width: '35%', textAlign: 'left'}}>Recipient</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>Rent exemption + remaining lamports<br />(all account lamports)</td>
+      <td>Rent sponsor</td>
+    </tr>
+    <tr>
+      <td>Compression incentive<br />(11,000 lamports)</td>
+      <td>Forester node</td>
+    </tr>
+  </tbody>
+</table>
+
+## Next Steps
+
+<Card
+  title=" Learn about all relevant actions to cMints"
+  icon="chevron-right"
+  color="#0066ff"
+  href="/compressible/mint-actions"
+  horizontal
+>
+</Card>