fix(tmux): resolve claude path for alias installations (#703) (#748)

Fix "Unable to attach mayor" timeout caused by claude being installed
as a shell alias rather than in PATH. Non-interactive shells spawned
by tmux cannot resolve aliases, causing the session to exit immediately.

Changes:
- Add resolveClaudePath() to find claude at ~/.claude/local/claude
- Apply path resolution in RuntimeConfigFromPreset() for claude preset
- Make hasClaudeChild() recursive (now hasClaudeDescendant()) to search
  entire process subtree as defensive improvement
- Update fillRuntimeDefaults() to use DefaultRuntimeConfig() for
  consistent path resolution

Fixes https://github.com/steveyegge/gastown/issues/703

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

internal/config/agents.go

@@ -327,10 +327,18 @@ func RuntimeConfigFromPreset(preset AgentPreset) *RuntimeConfig {
 		return DefaultRuntimeConfig()
 	}
 
-	return &RuntimeConfig{
+	rc := &RuntimeConfig{
 		Command: info.Command,
 		Args:    append([]string(nil), info.Args...), // Copy to avoid mutation
 	}
+
+	// Resolve command path for claude preset (handles alias installations)
+	// Uses resolveClaudePath() from types.go which finds ~/.claude/local/claude
+	if preset == AgentClaude && rc.Command == "claude" {
+		rc.Command = resolveClaudePath()
+	}
+
+	return rc
 }
 
 // BuildResumeCommand builds a command to resume an agent session.