fix: Array move ownership, selfhost -g flags, LSP workspace/symbol

Session 36: prevent UAF when Array is moved into a struct field (Nexus
headers), align selfhost cc flags with bootstrap debug/release, and add
workspace/symbol search to bux-lsp 0.6.

- Parser: zero headers after embedding so auto-drop is a no-op
- Request_WantsKeepAlive uses RequestHeader_Get again safely
- Selfhost: default -O0 -g; --release -O2 -DNDEBUG; BUX_CFLAGS
- LSP: workspace/symbol + smoke; version 0.6.0

Makefile

@@ -193,6 +193,9 @@ test-lsp: lsp
 	@echo "=== LSP references / rename smoke ==="
 	@chmod +x tools/smoke_lsp_rename.sh
 	@tools/smoke_lsp_rename.sh
+	@echo "=== LSP workspace/symbol smoke ==="
+	@chmod +x tools/smoke_lsp_workspace.sh
+	@tools/smoke_lsp_workspace.sh
 
 .PHONY: test-registry
 test-registry: build