Fix dynamic completion clobbering *1/*2/*3 and re-requiring per request

[bbatsov]

Two fixes to the dynamic (JS interop) completion path.

Fixes #5 - completion clobbered *1/*2/*3. Dynamic completion evaluates a probe in your REPL to introspect the object, and cljs.repl's default eval wrapper rotates the history vars after every eval - so each completion request overwrote *1 with the introspection result. cljs-eval now evaluates with a :wrap that skips that rotation (reusing cljs.repl/init-wrap-fn, which is exactly this). New test that establishes *1, completes, and asserts *1 survived.

Fixes #6 - re-required the introspection ns on every keystroke. js-properties-of-object required suitable.js-introspection on every completion request. The default path already loads it once via ensure-suitable-cljs-is-loaded, so that was a wasted eval round-trip per keystroke; the shadow path relied on it, so it now loads the ns once from its ensure-loaded step (guarded by a session flag) instead. Verified against both the Node and shadow-cljs integration tests.

Heads up: the Node integration test is a bit flaky (it occasionally fails to spawn the node process); unrelated to these changes, but a re-run clears it.

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