feat(extension): Chrome/Edge only + side panel chat tabs (v0.9.0)

- Remove Firefox build support (CI, Makefile, wxt config)
- Fix chrome.alarms undefined error (add 'alarms' permission)
- Add Chat tab to side panel connected to Studio API (/api/chat)
- Streaming SSE, tool calls, code blocks, thinking display
- Shared chat history with desktop Studio
- New lib/api.js client for extension chat endpoints

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

Makefile

@@ -9,7 +9,7 @@ WEB_DIR = web
 
 EXT_DIR = extension
 
-.PHONY: build install clean test test-short run scan fmt lint build-all deps vet frontend dev-desktop ext ext-chrome ext-firefox ext-zip
+.PHONY: build install clean test test-short run scan fmt lint build-all deps vet frontend dev-desktop ext ext-zip
 
 frontend:
 	cd $(WEB_DIR) && $(NPM) ci && $(NPM) run build
@@ -66,16 +66,10 @@ build-all: frontend
 	GOOS=windows GOARCH=arm64 $(GO) build -o dist/$(BINARY)-windows-arm64.exe ./cmd/muyue/
 
 ext:
-	cd $(EXT_DIR) && $(NPM) ci && $(NPM) run build && $(NPM) run build:firefox
-
-ext-chrome:
 	cd $(EXT_DIR) && $(NPM) ci && $(NPM) run build
 
-ext-firefox:
-	cd $(EXT_DIR) && $(NPM) ci && $(NPM) run build:firefox
-
 ext-zip:
-	cd $(EXT_DIR) && $(NPM) ci && $(NPM) run zip && $(NPM) run zip:firefox
+	cd $(EXT_DIR) && $(NPM) ci && $(NPM) run zip
 
 deps:
 	$(GO) mod tidy