refactor(chain)!: replace CanonicalIter with sans-io CanonicalizationTask

introduces `CanonicalizationTask` that implements canonicalization using a
request/response pattern, removing direct dependency on `ChainOracle`.

- add `CanonicalizationTask` with request/response pattern for chain queries
- track confirmed anchors to eliminate redundant queries
- handle direct vs transitive anchor determination
- return complete `CanonicalView` with correct chain positions
- add `LocalChain::handle_canonicalization_request` helper
- export `CanonicalizationTask`, `CanonicalizationRequest`, `CanonicalizationResponse`

BREAKING CHANGE: replaces direct `ChainOracle` querying in canonical iteration
with a new request/response pattern through `CanonicalizationTask`.

Author: oleonardolima