PROTO-835: fix: use precise ui amounts for sending and receiving token transfers

[Oighty]

This PR updates the V1 Solana Portal to use precise UI amounts when receiving and sending token transfers. Specifically, it updates the transfer_* and release_inbound_* instructions to work with the updated ext_swap program. The changes to swap facility are described in m0-platform/solana-m-extensions#65.

Additionally, the rounding behavior when minting M on received messages is changed to round up the principal amount so that we guarantee the extension program receives enough M principal to equate to the expected UI value. When burning the principal amount for the corresponding UI value is rounded down, to ensure we don't try to burn more M than received from the extension program. This could result in a slight gradual increase in excess M (10^-6 at a time per roundtrip), but it can be managed by adding M to the HubPortal on Ethereum or holding an amount on Solana for this purpose.

[Copilot]

Pull request overview

This PR updates the V1 Solana Portal to use precise UI amounts for token transfers, aligning with changes to the ext_swap program. The changes ensure correct rounding behavior: minting rounds UP to guarantee sufficient tokens, while burning rounds DOWN to prevent over-burning.

Changes:

• Receiving/minting now uses amount_to_principal_up to ensure users receive at least the bridged amount
• Sending/burning now uses amount_to_principal_down to protect users from over-burning
• Updated ext_swap IDL to work with the modified swap facility

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/unit/portal.test.ts	Added comprehensive test suite covering rounding behavior, fuzz tests, and edge cases for amount conversions
tests/test-utils.ts	Added conversion helper functions mirroring Rust logic for amount/principal transformations
programs/portal/src/instructions/transfer_extension.rs	Renamed variable from m_amount to m_principal for clarity
programs/portal/src/instructions/transfer.rs	Updated to use amount_to_principal_down for burning operations
programs/portal/src/instructions/release_inbound_extension.rs	Simplified to use UI amount directly instead of calculating from balance delta
programs/portal/src/instructions/release_inbound.rs	Changed from amount_to_principal_down to amount_to_principal_up for minting
programs/portal/idls/ext_swap.json	Updated IDL with new instruction, reformatted arrays, and modified account constraints
CLAUDE.md	Added new documentation file for Claude Code guidance

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