binding keys its thread-binding frame on var cells via (var x), so it
needed (var x) to compile. Added a the-var IR node that emits the embedded
var cell itself (vs var-ref, which derefs):
- ir.clj: the-var node.
- analyzer: 'var' added to handled; analyze-special resolves the symbol to
its var and emits the-var (uncompilable for a non-var, matching Clojure).
- backend: :the-var emits (quote cell) — the exact per-ctx cell var-get
keys on, so a compiled binding overrides + restores correctly.
- removed var from loader stateful-head? + host_iface special-names, and
binding from special-names so it expands+compiles.
Dynamic binding now compiles end-to-end (override/restore, and a compiled
fn reading the dynamic var under the binding) in both modes.
Gate green: conformance 267x3, fallback-zero 31/5, bootstrap-fixpoint
stage1==2==3, self-host, clojure-test-suite >=4034/67, features 78/78,
all unit + spec (state/metadata).