fix(emitter): loop in expression context via needsValue + IIFE wrapper

- Add needsValue parameter to emitExpr/emitSpecialForm to track expression context
- loop wraps in (proc(): CljVal = ... )() when needsValue=true
- Function call args, let/def values, vector/map literals pass needsValue=true
- emitProgramInternal passes needsValue=isLast for top-level forms
- Fixes: loop as function arg, loop in let RHS, loopResult at top level

.gitignore

@@ -26,3 +26,4 @@ test_single_debug.py
 src/tui_config
 experiments/native-lib/test_client/test_client
 experiments/wasm/tools/zig/
+lib/bring_http.nim