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.

cmd/root.go

@@ -0,0 +1,166 @@
+// Package cmd wires the cobra CLI: config resolution, database and Ollama
+// client lifecycles, and one file per subcommand.
+package cmd
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	"github.com/prdlk/gh-commit/internal/ai"
+	"github.com/prdlk/gh-commit/internal/db"
+	"github.com/prdlk/gh-commit/internal/gitx"
+	"github.com/prdlk/gh-commit/internal/ui"
+)
+
+// errAborted signals exit code 1 after the failure has already been printed.
+var errAborted = errors.New("aborted")
+
+type config struct {
+	host          string
+	model         string
+	timeout       time.Duration
+	auto          bool
+	push          bool
+	noAutoRefresh bool
+	debug         bool
+}
+
+var (
+	version = "dev"
+	cfg     config
+	store   *db.Store
+	client  *ai.Client
+
+	flagHost  string
+	flagModel string
+	flagAuto  bool
+	flagPush  bool
+)
+
+func envOr(key, def string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return def
+}
+
+func envBool(key string) bool { return os.Getenv(key) == "1" }
+
+func longHelp() string {
+	return fmt.Sprintf(`AI-powered scoped git commits driven by a local Ollama model.
+
+Scopes map Conventional Commit scope names to path prefixes. They are
+generated from the repository file tree by the model, stored in a local
+SQLite database, and auto-regenerate whenever .gitignore changes.
+Legacy .github/Repo.toml or scopes.json files are auto-migrated on first run.
+
+Database:
+  %s
+
+Environment:
+  GH_COMMIT_OLLAMA_HOST      Ollama server URL (default http://localhost:11434)
+  GH_COMMIT_MODEL            Model tag (default qwen3.5:2b)
+  GH_COMMIT_TIMEOUT          Per-request timeout in seconds (default 120)
+  GH_COMMIT_AUTO=1           Skip all confirmation prompts
+  GH_COMMIT_PUSH=1           Auto-push after commits
+  GH_COMMIT_NO_AUTO_REFRESH=1  Don't auto-regenerate scopes on .gitignore change
+  GH_COMMIT_DEBUG=1          Print raw model output on parse failure`, db.Path())
+}
+
+var rootCmd = &cobra.Command{
+	Use:           "gh-commit",
+	Short:         "AI-powered scoped git commits (Ollama)",
+	Long:          longHelp(),
+	Args:          cobra.NoArgs,
+	SilenceUsage:  true,
+	SilenceErrors: true,
+	CompletionOptions: cobra.CompletionOptions{
+		DisableDefaultCmd: true,
+	},
+	PersistentPreRunE: func(cmd *cobra.Command, _ []string) error {
+		cfg.host = envOr("GH_COMMIT_OLLAMA_HOST", "http://localhost:11434")
+		cfg.model = envOr("GH_COMMIT_MODEL", "qwen3.5:2b")
+		if flagHost != "" {
+			cfg.host = flagHost
+		}
+		if flagModel != "" {
+			cfg.model = flagModel
+		}
+		seconds := 120
+		if v, err := strconv.Atoi(envOr("GH_COMMIT_TIMEOUT", "120")); err == nil && v > 0 {
+			seconds = v
+		}
+		cfg.timeout = time.Duration(seconds) * time.Second
+		cfg.auto = envBool("GH_COMMIT_AUTO") || flagAuto
+		cfg.push = envBool("GH_COMMIT_PUSH") || flagPush
+		cfg.noAutoRefresh = envBool("GH_COMMIT_NO_AUTO_REFRESH")
+		cfg.debug = envBool("GH_COMMIT_DEBUG")
+		ui.AutoConfirm = cfg.auto
+
+		switch cmd.Name() {
+		case "version", "help":
+			return nil
+		}
+		s, err := db.Open()
+		if err != nil {
+			return err
+		}
+		store = s
+		if s.HadLegacyDuckDB {
+			ui.Warnf("Found a legacy DuckDB database (gh-commit.db) — it cannot be migrated; scopes will regenerate on 'gh commit init'")
+		}
+		return nil
+	},
+	RunE: runCommit,
+}
+
+// Execute runs the CLI, printing errors in red and exiting 1 on failure.
+func Execute(v string) {
+	version = v
+	rootCmd.Version = v
+	rootCmd.SetVersionTemplate("gh-commit {{.Version}}\n")
+	err := rootCmd.Execute()
+	if store != nil {
+		_ = store.Close()
+	}
+	if err != nil {
+		if !errors.Is(err, errAborted) {
+			ui.Errorf("%s", err)
+		}
+		os.Exit(1)
+	}
+}
+
+// requireGit asserts we're inside a git repo and returns its root path.
+func requireGit() (string, error) {
+	if !gitx.IsRepo() {
+		ui.Errorf("Not in a git repository")
+		return "", errAborted
+	}
+	return gitx.RepoRoot(), nil
+}
+
+// ensureAI builds the Ollama client and verifies server + model availability.
+func ensureAI() error {
+	if client != nil {
+		return nil
+	}
+	c := ai.New(cfg.host, cfg.model, cfg.timeout)
+	if err := c.EnsureReady(); err != nil {
+		return err
+	}
+	client = c
+	return nil
+}
+
+func init() {
+	rootCmd.PersistentFlags().BoolVar(&flagAuto, "auto", false, "skip all confirmation prompts")
+	rootCmd.PersistentFlags().BoolVar(&flagPush, "push", false, "auto-push after committing")
+	rootCmd.PersistentFlags().StringVar(&flagModel, "model", "", "override the Ollama model tag")
+	rootCmd.PersistentFlags().StringVar(&flagHost, "host", "", "override the Ollama server URL")
+}