Move docs to spec

spec/processor/Scanning.md

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+# Scanning
+
+Only blocks with finality, either actual or sufficiently probabilistic, are
+operated upon. This is referred to as a block with `CONFIRMATIONS`
+confirmations, the block itself being the first confirmation.
+
+For chains which promise finality on a known schedule, `CONFIRMATIONS` is set to
+`1` and each group of finalized blocks is treated as a single block, with the
+tail block's hash representing the entire group.
+
+For chains which offer finality, on an unknown schedule, `CONFIRMATIONS` is
+still set to `1` yet blocks aren't aggregated into a group. They're handled
+individually, yet only once finalized. This allows networks which form
+finalization erratically to not have to agree on when finalizations were formed,
+solely that the blocks contained have a finalized descendant.
+
+### Notability, causing a `Batch`
+
+`Batch`s are only created for blocks which it benefits to achieve ordering on.
+These are:
+
+- Blocks which contain transactions relevant to Serai
+- Blocks which in which a new multisig activates
+- Blocks in which a prior multisig retires
+
+### Waiting for `Batch` inclusion
+
+Once a `Batch` is created, it is expected to eventually be included on Serai.
+If the `Batch` isn't included within `CONFIRMATIONS` blocks of its creation, the
+scanner will wait until its inclusion before scanning
+`batch_block + CONFIRMATIONS`.