feat: add Go server implementation in go-server/

Full Go port of local-mcp with all core features. Copied from local-mcp-go
worktree to consolidate into single-branch repo (easier maintenance).
Architecture:
- internal/config:  Environment variable configuration
- internal/models:  Shared types (Instruction, Settings, AgentActivity, etc.)
- internal/db:      SQLite init with modernc.org/sqlite (pure Go, no CGo)
- internal/store:   Database operations + WakeupSignal + AgentTracker
- internal/events:  SSE broker for browser /api/events endpoint
- internal/mcp:     get_user_request MCP tool with 5s keepalive progress bars
- internal/api:     chi HTTP router with Bearer auth middleware
- main.go:          Entry point with auto port switching and Windows interactive banner
Dependencies:
- github.com/mark3labs/mcp-go@v0.46.0
- github.com/go-chi/chi/v5@v5.2.5
- modernc.org/sqlite@v1.47.0  (pure Go SQLite)
- github.com/google/uuid@v1.6.0
Static assets embedded via //go:embed static
Features matching Python:
- Same wait strategy: 50s with 5s progress keepalives
- Same hardcoded constants (DEFAULT_WAIT_SECONDS, DEFAULT_EMPTY_RESPONSE)
- Auto port switching (tries 8000-8009)
- Windows interactive mode (formatted banner on double-click launch)
Build:  cd go-server && go build -o local-mcp.exe .
Run:    ./local-mcp.exe
Binary size: ~18 MB (vs Python ~60+ MB memory footprint)
Startup:     ~10 ms (vs Python ~1-2s)

go-server/internal/api/status.go

@@ -0,0 +1,43 @@
+package api
+
+import (
+	"net/http"
+	"time"
+)
+
+func handleHealth() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		writeJSON(w, http.StatusOK, map[string]any{
+			"status":      "ok",
+			"server_time": time.Now().UTC().Format(time.RFC3339Nano),
+		})
+	}
+}
+
+func handleStatus(stores Stores) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		counts, _ := stores.Instructions.Counts()
+		latest, _ := stores.Agents.Latest()
+		cfg, _ := stores.Settings.Get()
+
+		resp := map[string]any{
+			"uptime_seconds":           int(time.Since(serverStartTime).Seconds()),
+			"queue_pending":            counts.PendingCount,
+			"queue_consumed":           counts.ConsumedCount,
+			"agent_stale_after_seconds": cfg.AgentStaleAfterSeconds,
+		}
+
+		if latest != nil {
+			isStale := time.Since(latest.LastSeenAt).Seconds() > float64(cfg.AgentStaleAfterSeconds)
+			resp["agent"] = map[string]any{
+				"agent_id":         latest.AgentID,
+				"last_fetch_at":    latest.LastFetchAt.Format(time.RFC3339Nano),
+				"last_result_type": latest.LastResultType,
+				"is_stale":         isStale,
+			}
+		}
+
+		writeJSON(w, http.StatusOK, resp)
+	}
+}
+