fix: skip git requirement for conversation/chat workflows

[buger]

Problem

StateMachineExecutionEngine.executeChecks() unconditionally requires a git repository. When isGitRepository is false, it immediately returns an error result with message "Not a git repository or no changes found" — even for chat/assistant workflows that have nothing to do with code review.

This prevents using the Visor SDK (runChecks()) for conversation-based workflows in environments without git, such as:

• Docker containers (node:*-slim images)
• Cloud Run / serverless functions
• CI environments running chat/assistant checks

Reproduction

import { loadConfig, runChecks } from '@probelabs/visor/sdk';

const config = await loadConfig('assistant.yaml');
const result = await runChecks({
  config,
  checks: ['chat'],
  executionContext: {
    conversation: { /* ... */ },
  },
});

// In a non-git environment:
// result.reviewSummary.issues[0].message === "Not a git repository or no changes found"
// The onCheckComplete hook never fires
// The chat workflow never executes

Fix

When an executionContext.conversation is present, the workflow is a chat/assistant interaction — not a code review — and doesn't need git. The fix adds a single condition to skip the git error when a conversation context exists:

const hasConversation = !!(this.executionContext as any)?.conversation;
if (!repositoryInfo.isGitRepository && !hasConversation) {
  return this.createErrorResult(...);
}

The git analysis still runs (providing empty repository info), but execution continues to the check workflows instead of short-circuiting.

Test plan

• Existing tests pass (no behavior change for code review workflows)
• runChecks() with a conversation context succeeds in a non-git directory
• runChecks() without a conversation context still fails in a non-git directory (existing behavior preserved)

🤖 Generated with Claude Code