feat(AggLayer bridge-out e2e #2): store Local Exit Tree in AggLayerBridge contract and update it upon B2AGG consumption

[mmagician]

Implements Local Exit Tree (LET) frontier management in the bridge_out component.

Changes:

• store the frontier (32 nodes) of the Local Exit Tree in the bridge contract
  • uses a double-array data structure for convenience, with the map as the underlying storage slot
• store the root as two value slots (low, high)
• store the number of leaves in a single value slot
• after computing the leaf value in feat(AggLayer bridge-out e2e #1): process bridging-out data and load LeafData to memory #2425, process the leaf:
  1. load the existing LET frontier to memory
  2. call append_and_update_frontier to update the frontier in-memory and obtain the root
  3. write back the frontier from memory to storage
  4. save the obtained root and number of leaves to storage

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[cursor]

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[Copilot]

Pull request overview

Implements Local Exit Tree (LET) persistence for AggLayer bridge-out by storing the LET frontier and associated metadata in the AggLayerBridge account storage, and validating the resulting Local Exit Root against Solidity-generated vectors.

Changes:

• Add dedicated bridge account storage slots for LET root (lo/hi) and leaf count, alongside the existing LET map slot.
• Update bridge_out.masm to load the LET frontier from storage, append a leaf via append_and_update_frontier, and persist the updated frontier/root/leaf-count back to storage.
• Extend Solidity/Rust compatibility vectors and tests to include destination parameters and amounts, and assert the computed Local Exit Root matches Solidity.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
crates/miden-testing/tests/agglayer/mod.rs	Exposes mmr_frontier module for cross-test reuse.
crates/miden-testing/tests/agglayer/mmr_frontier.rs	Makes Solidity vector JSON/static data public and extends vector schema (amounts + destination fields).
crates/miden-testing/tests/agglayer/bridge_out.rs	Adds a test asserting Local Exit Root after B2AGG processing matches Solidity vector root.
crates/miden-agglayer/src/lib.rs	Extends bridge account builder with LET root/leaf-count value slots in addition to the LET map slot.
crates/miden-agglayer/solidity-compat/test/MMRTestVectors.t.sol	Updates vector generation to DepositContractV2, includes destination params and amounts, and generates leaf values via getLeafValue.
crates/miden-agglayer/solidity-compat/test-vectors/mmr_frontier_vectors.json	Updates embedded vectors to new leaf/root set and includes amounts + destination fields.
crates/miden-agglayer/solidity-compat/foundry.lock	Adds OZ upgradeable dependency required by updated Solidity contracts.
crates/miden-agglayer/asm/bridge/bridge_out.masm	Implements LET frontier load/append/store, plus root and leaf-count persistence.

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[partylikeits1983]

I wish these imports were autoformatted to be in alphabetical order since there are so many imports. My old masm formatter would do this, but its out of date with the latest masm syntax.

[partylikeits1983]

Looks good! Just want to figure out what is going on here: https://github.com/0xMiden/miden-base/pull/2424/changes#r2816492107

before I leave an approval, but otherwise this is great!

[partylikeits1983]

Looks good! Thanks for addressing https://github.com/0xMiden/miden-base/pull/2424/changes#r2816492107