Add changelog entry

Author: jasagredo

ouroboros-consensus/changelog.d/20260216_123105_javier.sagredo_cleanup_chainsel.md

@@ -0,0 +1,41 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+For top level release notes, leave all the headers commented out.
+-->
+
+<!--
+### Patch
+
+- A bullet item for the Patch category.
+
+-->
+<!--
+### Non-Breaking
+
+- A bullet item for the Non-Breaking category.
+
+-->
+
+### Breaking
+
+- Cleanup Chain selection:
+  - Removed `Ouroboros.Consensus.Fragment.Validated` as it was only an
+    indirection over `Ouroboros.Consensus.Fragment.ValidatedDiff`.
+  - Initial chain selection now also performs the commit on the forker and
+    returns only the selected fragment of headers.
+  - Deleted `ChainAndLedger` as it was an unnecessary indirection.
+  - Deleted `validateCandidate` as it was an unnecessary indirection to
+    `ledgerValidateCandidate` which was now renamed to `validatedCandidate`.
+- Cleanup LedgerDB:
+  - `validateFork` allows for `l` other than `ExtLedgerState`.
+  - `validateFork` expects a non-empty list of headers.
+  - `ValidateArgs` now expects an `l` that can be different to `ExtLedgerState`.
+  - `Ap` has been simplified to monomorphize the constraints. `applyBlock` and
+    related functions now run on an appropriate monad.
+  - Classes `ThrowsLedgerErrors` and `ResolvesBlocks` have been deletes as
+    unnecessary.
+  - `MonadBase` scattered constraints have been removed as unnecessary.
+  - `AnnLedgerError` carries a point to the latest valid block instead of a
+    forker.