refactor(instance): remove container image label support (#51)

* refactor(instance): remove container image label support

Current behavior:
Container runtime flags could be configured via OCI image labels
(io.headjack.init, io.headjack.podman.flags, io.headjack.docker.flags).
The instance manager fetched image metadata from the registry and merged
label-based flags with config file flags.

New behavior:
Runtime flags are now exclusively configured via the config file
(runtime.flags in config.yaml). The registry package and all label
parsing code have been removed. This simplifies the codebase and
removes the dependency on registry metadata fetching.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(docs): remove labels.md from sidebar

Current behavior:
Sidebar referenced the deleted labels.md file, causing Docusaurus build
to fail on Cloudflare.

New behavior:
Sidebar only references the overview page for container images.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: jmgilman

docs/docs/reference/images/labels.md

@@ -113,7 +113,3 @@ For complete image specifications, see the Dockerfiles in the repository:
 - [Base Dockerfile](https://github.com/GilmanLab/headjack/blob/master/images/base/Dockerfile)
 - [Systemd Dockerfile](https://github.com/GilmanLab/headjack/blob/master/images/systemd/Dockerfile)
 - [Docker-in-Docker Dockerfile](https://github.com/GilmanLab/headjack/blob/master/images/dind/Dockerfile)
-
-## See Also
-
-- [OCI Labels](labels.md) - Labels for custom image configuration

docs/docs/reference/images/overview.md

@@ -118,7 +118,6 @@ const sidebars: SidebarsConfig = {
           },
           items: [
             'reference/images/overview',
-            'reference/images/labels',
           ],
         },
       ],

docs/sidebars.ts

@@ -43,17 +43,5 @@ STOPSIGNAL SIGRTMIN+3
 # Volume for cgroups (required for systemd)
 VOLUME ["/sys/fs/cgroup"]
 
-# =============================================================================
-# Headjack Runtime Configuration Labels
-# =============================================================================
-
-# These labels inform Headjack how to run the image:
-# - io.headjack.init: Command to run as PID 1 (overrides "sleep infinity" default)
-# - io.headjack.podman.flags: Space-separated key=value pairs for Podman flags
-# - io.headjack.docker.flags: Space-separated key=value pairs for Docker flags
-LABEL io.headjack.init="/lib/systemd/systemd"
-LABEL io.headjack.podman.flags="systemd=always"
-LABEL io.headjack.docker.flags="privileged=true cgroupns=host volume=/sys/fs/cgroup:/sys/fs/cgroup:rw"
-
 # systemd as init system
 CMD ["/lib/systemd/systemd"]

images/systemd/Dockerfile

@@ -21,7 +21,6 @@ import (
 	"github.com/jmgilman/headjack/internal/git"
 	"github.com/jmgilman/headjack/internal/instance"
 	"github.com/jmgilman/headjack/internal/multiplexer"
-	"github.com/jmgilman/headjack/internal/registry"
 )
 
 // baseDeps lists the external binaries that must always be available.
@@ -176,19 +175,16 @@ func initManager() error {
 	// Use tmux as the terminal multiplexer
 	mux := multiplexer.NewTmux(executor)
 
-	// Create registry client for fetching image metadata
-	regClient := registry.NewClient(registry.ClientConfig{})
-
 	// Map runtime name to RuntimeType
 	runtimeType := runtimeNameToType(runtimeName)
 
-	// Parse config flags for merging with image label flags
+	// Parse config flags
 	configFlags, err := getConfigFlags()
 	if err != nil {
 		return err
 	}
 
-	mgr = instance.NewManager(store, runtime, opener, mux, regClient, instance.ManagerConfig{
+	mgr = instance.NewManager(store, runtime, opener, mux, instance.ManagerConfig{
 		WorktreesDir: worktreesDir,
 		LogsDir:      logsDir,
 		RuntimeType:  runtimeType,

internal/cmd/root.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"sort"
-	"strings"
 )
 
 // Flags represents runtime flags as a key-value map.
@@ -55,61 +54,6 @@ func FromConfig(cfg map[string]any) (Flags, error) {
 	return result, nil
 }
 
-// FromLabel parses a space-separated string of key=value pairs into Flags.
-// Format: "key1=value1 key2=value2 boolkey=true barekey"
-//
-// Rules:
-//   - "key=value" → string value
-//   - "key=true" or "key=false" → bool value
-//   - "key" (bare, no =) → bool true
-//   - Repeated keys become []string (e.g., "vol=/a vol=/b" → {"vol": ["/a", "/b"]})
-//   - Values containing = are handled correctly (splits on first = only)
-func FromLabel(label string) (Flags, error) {
-	result := make(Flags)
-	if label == "" {
-		return result, nil
-	}
-
-	for _, part := range strings.Fields(label) {
-		key, value, hasEquals := strings.Cut(part, "=")
-		if key == "" {
-			continue // Skip empty keys
-		}
-
-		if !hasEquals {
-			// Bare key treated as boolean true (e.g., "privileged")
-			result[key] = true
-			continue
-		}
-
-		// Check for boolean string values
-		switch strings.ToLower(value) {
-		case "true":
-			result[key] = true
-			continue
-		case "false":
-			result[key] = false
-			continue
-		}
-
-		// Handle repeated keys by converting to array
-		if existing, ok := result[key]; ok {
-			switch e := existing.(type) {
-			case string:
-				result[key] = []string{e, value}
-			case []string:
-				result[key] = append(e, value)
-			default:
-				// Overwrite non-string values (e.g., bool) with the new string
-				result[key] = value
-			}
-		} else {
-			result[key] = value
-		}
-	}
-	return result, nil
-}
-
 // Merge combines two Flags maps with override taking precedence.
 // Keys in override replace keys in base.
 func Merge(base, override Flags) Flags {