new-op

You want to add Op::$1 to the outl tree CRDT. MANDATORY checklist:

1. Define the variant in crates/outl-core/src/op.rs

$1 {
    node: NodeId,
    // ... op fields
    // CRITICAL: include `old_*` fields for undo.
    // Without old_*, undo_op cannot revert.
}

2. Implement do_op in crates/outl-core/src/tree.rs

• Fill old_* in the LogOp before applying the mutation.
• If the op can violate an invariant (cycle, etc), check first and treat as a no-op on materialization (but the op still goes to the log).

3. Implement undo_op

• Revert using the old_* fields of the LogOp.
• Idempotency: undo of an op that was never applied must be a no-op.

4. Update serialization

• Verify that serde derive already covers it. If there's a binary field, ensure base64 or bincode.
• Add conversion to the SQLite schema in storage/sqlite.rs if the op has extra fields.

5. Mandatory tests (in crates/outl-core/tests/)

• Convergence: 3 replicas apply the op in different orders → same final state.
• Idempotency: applying 2x = applying 1x.
• Reordering: a late-arriving op forces a correct undo/replay.
• Interaction with Move: an op concurrent with a Move on the same node converges.

6. Document in docs/crdt.md

• Add a paragraph in the "Operations" section describing semantics.
• Add a concurrent example if the op has non-obvious interactions.

7. Pre-flight before PR

• cargo fmt
• cargo clippy -- -D warnings
• cargo test -p outl-core
• 100% coverage on the new branches in do_op/undo_op
• Invoke the crdt-invariant-checker agent
• Invoke the paper-verifier agent if the op has an analog in the paper

Do not skip steps. A new op that breaks convergence destroys trust in outl.