fix: Prevent features from getting stuck in in_progress after server restart

- Add graceful shutdown handler that marks running features as 'interrupted'
  before server exit (SIGTERM/SIGINT)
- Add 30-second shutdown timeout to prevent hanging on exit
- Add orphan detection to identify features with missing branches
- Add isFeatureRunning() for idempotent resume checks
- Improve resumeInterruptedFeatures() to handle features without saved context
- Add 'interrupted' status to FeatureStatusWithPipeline type
- Replace console.log with proper logger in auto-mode-service
- Add comprehensive unit tests for all new functionality (15 new tests)

Fixes #696

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

libs/types/src/pipeline.ts

@@ -22,6 +22,7 @@ export type PipelineStatus = `pipeline_${string}`;
 export type FeatureStatusWithPipeline =
   | 'backlog'
   | 'in_progress'
+  | 'interrupted'
   | 'waiting_approval'
   | 'verified'
   | 'completed'