feat(dbt+ai): build out cubedbt and cubeai packages (Package 4, PDF §549/§551)

cubedbt: DBT runtime that reads CZYX-stored translation rules and patches
them into a code cache to execute mimicked behavior. TranslationRule (CZYX
Variant record in c220 band) maps an op-class to a replacement bytecode
fragment; CodeCache patches an original CodeCell under eligible rules and
writes the result as a Variant (preserving behavior descriptors), and
DbRuntime.mimic() fetches -> patches -> runs in the real Vm, proving
're-run or modify behavior without the original binary'.

cubeai: models over cube-stored traces/graphs to classify blocks
(Computation/Branch/CallTrampoline/IoSection/Sequence from the op-class
histogram + behavior descriptors) and suggest new code sequences as
cubedbt TranslationRules (persisted into the c220 rule band, discoverable
by DbRuntime). End-to-end: trace -> classify -> suggest -> mimic.

Both crates are dependency-free and operate on the real CubeStore/CodeCell/
Vm/Behavior types, so they are exercisable today on HashBackend and slot
into ConcurrentStore later without an API change. ./check quick green:
cubedbt 4 tests, cubeai 5 tests, full workspace green.

cubeai/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "cubeai"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+description = "CUBELinux-2 AI layer: models that operate on cube-stored traces/graphs to classify blocks, infer higher-level operations, and suggest new code sequences (PDF Package 4, §551)."
+
+[dependencies]
+cubecoords = { path = "../cubecoords" }
+cubestore = { path = "../cubestore" }
+cubecode = { path = "../cubecode" }
+cubedbt = { path = "../cubedbt" }