feat(amm): add admin authority and UpdateConfig instruction

[0x-r4bbit]

Add an admin authority to the AMM config so configuration can be changed after initialization. AmmConfig gains an authority field, set by Initialize, and a new UpdateConfig instruction lets that admin change config values.

UpdateConfig is access-controlled: the authority account must equal the stored config.authority and be passed authorized (signed). Both fields are optional — token_program_id updates the chained-call token program, and new_authority transfers admin control to a different account. Without this gate any caller could repoint the AMM at a malicious token program.

[Copilot]

Pull request overview

This PR adds an admin authority to the AMM’s singleton config account and introduces a new UpdateConfig instruction so the token program ID and/or admin authority can be changed after initialization, with signature-based access control.

Changes:

• Extend AmmConfig with an authority: AccountId field and update Initialize to set it.
• Add UpdateConfig instruction + program implementation that only allows the configured authority (signed) to mutate config fields.
• Update guest method handlers, IDL artifacts, and integration/unit tests to cover the new config layout and access control behavior.

Reviewed changes

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

Show a summary per file

File	Description
programs/integration_tests/tests/amm.rs	Adds admin key/id helpers and new integration tests covering UpdateConfig behavior and authority handoff.
programs/amm/src/update_config.rs	Implements update_config handler with authority checks; adds unit tests for happy path and failure cases.
programs/amm/src/tests.rs	Updates AMM test scaffolding to include the new authority field in config data.
programs/amm/src/lib.rs	Exposes the new update_config module.
programs/amm/src/initialize.rs	Extends initialize to store authority in config; updates tests accordingly.
programs/amm/methods/guest/src/bin/amm.rs	Updates the guest instruction interface for Initialize and adds guest handler for UpdateConfig.
programs/amm/core/src/lib.rs	Updates the core instruction enum and AmmConfig struct to include authority; documents UpdateConfig.
artifacts/amm-idl.json	Updates IDL to include the new initialize arg and new update_config instruction + updated config type.

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