Add C-family (Objective-C/C/C++) declaration parsing support

Extends symbol extraction to mixed Swift+C-family packages via clangd
multiplexing through sourcekit-lsp: new CFamilyDeclarationParser,
CompilationDatabaseWriter, ObjectiveCShimWriter, SourceLanguage detection,
PathFilter, and ShapeSnapshot, plus a shared DeclarationParser contract and
build/test scripts.

build.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+LIBAVCODEC_MAJOR=$(pkg-config --modversion libavcodec 2>/dev/null | cut -d. -f1)
+export LIBAVCODEC_MAJOR="${LIBAVCODEC_MAJOR:-0}"
+OUTFILE=$(mktemp /tmp/build_output_XXXXXX.txt)
+swift build >"$OUTFILE" 2>&1
+STATUS=$?
+grep -E "^/home/$(whoami)/Projects/CodeMapper/Sources/.*error:" "$OUTFILE" | sed "s|/home/$(whoami)/Projects/CodeMapper/||" | head -10
+if [ $STATUS -eq 0 ]; then
+    echo "Build succeeded."
+else
+    echo "Build FAILED. Full output: $OUTFILE"
+fi