refactor: migrate MICRO_PIP to fine-grained feature flags

Replace monolithic MICRO_PIP/PIP_MICRO with granular flags:

Feature flags (CMake options + platform auto-detection):
- PIP_NO_FILESYSTEM, PIP_NO_THREADS, PIP_NO_SOCKET
- PIP_NO_PROCESS, PIP_NO_DYNLIB, PIP_NO_FFT, PIP_NO_SERIAL

Embedded optimization flag:
- PIP_EMBEDDED (auto-set for Pico SDK and FreeRTOS)
  Controls buffer sizes, time stubs, terminal fallback, init stubs

Platform blocks in CMakeLists.txt:
- Pico SDK: auto-disables FS, PROCESS, DYNLIB, FFT, SERIAL;
  conditionally disables THREADS (no FreeRTOS) and SOCKET (no LWIP)
- FreeRTOS: auto-disables FS, PROCESS, DYNLIB, FFT, SERIAL;
  conditionally disables SOCKET (no LWIP)
- Android: auto-disables PROCESS, DYNLIB, FFT

Updated 96 files across libs/, utils/, tests/, and CMakeLists.txt.
Builds verified for Linux (547 tests pass) and Pico SDK (100%).
Removed all MICRO_PIP and PIP_MICRO references (0 remaining).

libs/main/serialization/pivaluetree_conversions.cpp

@@ -43,11 +43,15 @@ PIString mask(const PIString & str) {
 }
 
 PIString overrideFile(PIString path) {
+#ifndef PIP_NO_FILESYSTEM
 	if (path.isEmpty()) return {};
 	PIFile::FileInfo fi(path);
 	auto ext = fi.extension();
 	path.insert(path.size_s() - ext.size_s() - (ext.isEmpty() ? 0 : 1), ".override");
 	return path;
+#else
+	return path;
+#endif
 }
 
 
@@ -138,7 +142,9 @@ PIValueTree PIValueTreeConversions::fromText(PIIODevice * device) {
 	PIMap<PIString, PIString> substitutions;
 	if (!device) return ret;
 	PIString base_path;
+#ifndef PIP_NO_FILESYSTEM
 	if (device->isTypeOf<PIFile>()) base_path = PIFile::FileInfo(device->path()).dir().replaceAll('\\', '/');
+#endif
 	PIIOTextStream ts(device);
 	PIString line, comm;
 	PIVariant value;
@@ -211,10 +217,12 @@ PIValueTree PIValueTreeConversions::fromText(PIIODevice * device) {
 			line.cutLeft(1).trim();
 			if (path.front() == "include") {
 				PIString include = line.trimmed();
+#ifndef PIP_NO_FILESYSTEM
 				if (!PIFile::FileInfo(include).isAbsolute()) {
 					include = base_path + "/" + include.replaceAll('\\', '/');
 					include.replaceAll("//", '/');
 				}
+#endif
 				PIValueTree inc_vt = PIValueTreeConversions::fromTextFile(include);
 				inc_vt.forEachRecursive(
 					[&substitutions](const PIValueTree & v, const PIString & fn) { substitutions[fn] = v.value().toString(); });
@@ -345,6 +353,9 @@ PIValueTree PIValueTreeConversions::fromText(const PIString & str) {
 
 
 PIValueTree PIValueTreeConversions::fromJSONFile(const PIString & path) {
+#ifdef PIP_NO_FILESYSTEM
+	return PIValueTree();
+#else
 	auto ret = PIValueTreeConversions::fromJSON(PIJSON::fromJSON(PIString::fromUTF8(PIFile::readAll(path))));
 	auto ofp = overrideFile(path);
 	if (PIFile::isExists(ofp)) {
@@ -352,10 +363,14 @@ PIValueTree PIValueTreeConversions::fromJSONFile(const PIString & path) {
 		ret.merge(override_vt);
 	}
 	return ret;
+#endif
 }
 
 
 PIValueTree PIValueTreeConversions::fromTextFile(const PIString & path) {
+#ifdef PIP_NO_FILESYSTEM
+	return PIValueTree();
+#else
 	PIFile f(path, PIIODevice::ReadOnly);
 	auto ret = PIValueTreeConversions::fromText(&f);
 	auto ofp = overrideFile(path);
@@ -365,18 +380,27 @@ PIValueTree PIValueTreeConversions::fromTextFile(const PIString & path) {
 		ret.merge(override_vt);
 	}
 	return ret;
+#endif
 }
 
 
 bool PIValueTreeConversions::toJSONFile(const PIString & path, const PIValueTree & root, Options options) {
+#ifdef PIP_NO_FILESYSTEM
+	return false;
+#else
 	auto d      = toJSON(root, options).toJSON(PIJSON::Tree).toUTF8();
 	int written = PIFile::writeAll(path, d);
 	return written == d.size_s();
+#endif
 }
 
 
 bool PIValueTreeConversions::toTextFile(const PIString & path, const PIValueTree & root, Options options) {
+#ifdef PIP_NO_FILESYSTEM
+	return false;
+#else
 	auto d      = toText(root, options).toUTF8();
 	int written = PIFile::writeAll(path, d);
 	return written == d.size_s();
+#endif
 }