feat: scoring and frecency (#37)

Enhance lookup mechanics and priority propagation (`spec/lookup.go`)
Remove the requirement of typing a leading `-` when searching for
options, allowing flag suggestions to surface naturally during input
Accurately forward the `Priority` field from registry specs into the
`Suggestion` struct so the scoring engine evaluates relevance properly

Integrate scoring into the main suggestion pipeline
(`root/suggestions.go`)
Collect context signals using `scoring.CollectSignals(cwd, query,
rootCmd, store)` with the live working directory retrieved from
`spec.GetCWD()`
Pass the entire deduplicated list across spec, history and AI items
through `scoring.Score(deduped, signals)` to compute scores and sort by
descending order before rendering on screen

Record execution history in Frecency Store (`root/wrapper.go`)
Save the last executed command to `lastSubmittedCommand` whenever Enter
is pressed or a suggestion is selected
Trigger `store.Record(...)` asynchronously within the `IRIS_CMD_STOP`
hook using a dedicated goroutine guarded by panic recovery and timeout
limits, preventing blocks on the main shell thread

Optimize workspace identification for AI
(`internal/ai/context_provider.go`)
Use `workspace.DetectCached(cwd)` to instantly fetch ecosystem context
across Git, Node, Go, Rust, Python and Docker alongside active git
branch state
This caching mechanism avoids redundant subprocess execution when
outside git repositories, significantly speeding up prompt context
generation

internal/scoring/signals_test.go

@@ -0,0 +1,35 @@
+package scoring
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestCollectSignals(t *testing.T) {
+	tmpDir := t.TempDir()
+	_ = os.WriteFile(filepath.Join(tmpDir, "package.json"), []byte("{}"), 0644)
+
+	dbPath := filepath.Join(tmpDir, "history.db")
+	store, err := NewFrecencyStore(dbPath)
+	if err != nil {
+		t.Fatalf("NewFrecencyStore failed: %v", err)
+	}
+	defer store.Close()
+
+	_ = store.Record(context.Background(), "npm run dev", tmpDir)
+	_ = store.Record(context.Background(), "npm test", "/other/dir")
+
+	signals := CollectSignals(context.Background(), tmpDir, "npm", "npm", store)
+
+	if !signals.Workspace.HasNodeProject {
+		t.Error("expected HasNodeProject to be true in collected signals")
+	}
+	if len(signals.LocalFrecency) != 1 || signals.LocalFrecency[0].Cmd != "npm run dev" {
+		t.Errorf("expected local frecency to contain 'npm run dev', got %v", signals.LocalFrecency)
+	}
+	if len(signals.GlobalFrecency) != 2 {
+		t.Errorf("expected global frecency to contain 2 entries, got %d", len(signals.GlobalFrecency))
+	}
+}