[FEATURE] #880 - Create BatchExecutionMemory service for cross-task learning summaries

[stephanj]

Parent Issue

Part of #880 — Introduce Batch-Level Learning and Strategy Memory

Context

Each task starts with a fresh conversation context. There is no mechanism to pass execution learnings from completed tasks to subsequent ones. A BatchExecutionMemory service would collect per-task summaries and make them available for injection into downstream task prompts.

Task

Create a BatchExecutionMemory service that accumulates learning from completed tasks within a batch run.

Key Changes

1. Create BatchExecutionMemory service:

   public class BatchExecutionMemory {
       /** Record what a completed task learned/produced */
       void recordTaskCompletion(String taskId, TaskLearningEntry entry);
       
       /** Get summarized learning context for injection into next task */
       String getSummarizedContext(int maxChars);
       
       /** Get entries for specific dependency tasks */
       List<TaskLearningEntry> getEntriesForTasks(List<String> taskIds);
       
       /** Clear at batch start */
       void clear();
   }

2. Create TaskLearningEntry model:

   @Data
   public class TaskLearningEntry {
       String taskId;
       String taskTitle;
       String executionSummary;      // what was done (from finalSummary)
       List<String> filesModified;   // what files changed
       List<String> patternsFound;   // extracted patterns/notes
       String strategyUsed;          // e.g., "used web search", "refactored via AST"
       TaskResultStatus status;      // success/fail
       long executionTimeMs;
       String errorNote;             // what went wrong (if failed)
   }

3. Populate from task completion:

   • On onTaskCompleted(): re-read TaskSpec from SpecService to get finalSummary, implementationNotes
   • Extract structured data into TaskLearningEntry
   • On onTaskSkipped()/failed: record failure patterns

4. Summarization strategy:

   • Most recent N tasks get full entries
   • Older tasks get one-line summaries
   • Total context capped at configurable maxLearningContextLength
   • Failed tasks always included (so downstream can avoid same mistakes)

Files to Create

• src/main/java/com/devoxx/genie/service/spec/BatchExecutionMemory.java (new)
• src/main/java/com/devoxx/genie/model/spec/TaskLearningEntry.java (new)

Dependencies

• Requires: TaskExecutionMetrics ([FEATURE] #880 - Create TaskExecutionMetrics model for per-task telemetry #910)

Acceptance Criteria

• Learning entries captured for completed and failed tasks
• getSummarizedContext() returns a token-budget-respecting summary
• Older entries compressed to one-liners, recent entries full
• Failed tasks always included in summary
• Memory cleared between batch runs
• Thread-safe for potential parallel execution