Emit :throw as jolt-throw (Scheme raise of the raw jolt value, matching the
Janet compiled back end's (error v) — no envelope, so catch binds it directly).
Emit :try as guard (catch; the class is dropped in the IR, so it's catch-all)
plus dynamic-wind for finally. ex-info is a native-op building the tagged jolt
map {:jolt/type :jolt/ex-info :message :data :cause}, so the ex-data/ex-message/
ex-cause tier fns read it over jolt-get for free.
Prelude emit reach 303 -> 334/355 (:throw and :try gaps close). Subset probe
619 -> 632/632 compiled, 0 divergences (throw/try/ex-info pull 13 corpus cases
into the subset). emit-test 94/94 (added 11 throw/try/ex-info cases + uncaught
exits non-zero). Full gate green.
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