feat: rewrite gh-commit in Go with local Ollama backend

Replaces the Python/Crush/DuckDB implementation with a CGO-free Go binary:
cobra CLI, modernc.org/sqlite storage, huh/lipgloss UI, and speed-tuned raw
/api/generate calls (think:false, keep_alive, capped num_predict) against a
local qwen3.5:2b. Ships as a gh extension via cli/gh-extension-precompile.

internal/db/store_test.go

@@ -0,0 +1,103 @@
+package db
+
+import (
+	"reflect"
+	"testing"
+)
+
+func openTestStore(t *testing.T) *Store {
+	t.Helper()
+	t.Setenv("XDG_DATA_HOME", t.TempDir())
+	s, err := Open()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+	return s
+}
+
+func TestSaveAndReadScopes(t *testing.T) {
+	s := openTestStore(t)
+	scopes := map[string][]string{
+		"core": {"internal/", "main.go"},
+		"docs": {"README.md"},
+	}
+
+	if has, _ := s.HasScopes("/repo"); has {
+		t.Fatal("fresh store should have no scopes")
+	}
+	if err := s.SaveScopes("/repo", "repo", scopes, "hash1"); err != nil {
+		t.Fatal(err)
+	}
+	if has, _ := s.HasScopes("/repo"); !has {
+		t.Fatal("scopes should exist after save")
+	}
+	got, err := s.Scopes("/repo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(got, scopes) {
+		t.Errorf("got %#v, want %#v", got, scopes)
+	}
+
+	hash, present, err := s.StoredGitignoreHash("/repo")
+	if err != nil || !present || hash != "hash1" {
+		t.Errorf("want (hash1, true), got (%q, %v, %v)", hash, present, err)
+	}
+}
+
+func TestSaveScopesReplacesExisting(t *testing.T) {
+	s := openTestStore(t)
+	if err := s.SaveScopes("/repo", "repo", map[string][]string{"old": {"a/"}}, "h1"); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.SaveScopes("/repo", "repo", map[string][]string{"new": {"b/"}}, "h2"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := s.Scopes("/repo")
+	want := map[string][]string{"new": {"b/"}}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("old scopes must be cascade-deleted; got %#v", got)
+	}
+	if hash, _, _ := s.StoredGitignoreHash("/repo"); hash != "h2" {
+		t.Errorf("hash not updated: %q", hash)
+	}
+}
+
+func TestDeleteRepoCascades(t *testing.T) {
+	s := openTestStore(t)
+	if err := s.SaveScopes("/repo", "repo", map[string][]string{"core": {"a/"}}, "h"); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.DeleteRepo("/repo"); err != nil {
+		t.Fatal(err)
+	}
+	if has, _ := s.HasScopes("/repo"); has {
+		t.Error("scopes must be gone after repo delete")
+	}
+	var n int
+	if err := s.db.QueryRow(`SELECT COUNT(*) FROM scope_paths`).Scan(&n); err != nil || n != 0 {
+		t.Errorf("scope_paths rows must cascade away, got %d (%v)", n, err)
+	}
+}
+
+func TestStoredGitignoreHashUnknownRepo(t *testing.T) {
+	s := openTestStore(t)
+	if _, present, err := s.StoredGitignoreHash("/nowhere"); err != nil || present {
+		t.Errorf("unknown repo: want (false, nil), got (%v, %v)", present, err)
+	}
+}
+
+func TestListRepos(t *testing.T) {
+	s := openTestStore(t)
+	if err := s.SaveScopes("/a", "a", map[string][]string{"x": {"x/"}, "y": {"y/"}}, ""); err != nil {
+		t.Fatal(err)
+	}
+	repos, err := s.ListRepos()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(repos) != 1 || repos[0].Name != "a" || repos[0].ScopeCount != 2 {
+		t.Errorf("got %#v", repos)
+	}
+}