feat: load context files as system prompt for higher priority

Context files from .automaker/context/ (CLAUDE.md, CODE_QUALITY.md, etc.)
are now passed as system prompt instead of prepending to user prompt.
This ensures the agent follows project-specific rules like package manager
preferences (pnpm vs npm) and coding conventions.

Changes:
- Add getContextDir() utility to automaker-paths.ts
- Add loadContextFiles() method to load .md/.txt files from context dir
- Pass context as systemPrompt in executeFeature() and followUpFeature()
- Add debug logging to confirm system prompt is provided

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

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

apps/server/src/lib/automaker-paths.ts

@@ -53,6 +53,13 @@ export function getImagesDir(projectPath: string): string {
   return path.join(getAutomakerDir(projectPath), "images");
 }
 
+/**
+ * Get the context files directory for a project (user-added context files)
+ */
+export function getContextDir(projectPath: string): string {
+  return path.join(getAutomakerDir(projectPath), "context");
+}
+
 /**
  * Get the worktrees metadata directory for a project
  */