Parent: #1235
Blocked by: #1239

Summary

Implement result aggregation and graph lifecycle management (resume paused graphs, retry failed tasks).

Branch: feat/m33/orchestration-aggregator

Deliverables

New files

• crates/zeph-core/src/orchestration/aggregator.rs — Aggregator trait + LlmAggregator impl

Modified files

• crates/zeph-core/src/orchestration/command.rs — add /plan resume, /plan retry

Aggregator

• Concatenates TaskResult.output from all completed tasks
• Calls LLM with aggregator_max_tokens to synthesize coherent final response
• Handles graphs with skipped tasks (mentions them in synthesis)
• Uses planner_model config (or agent's primary model)

Resume/Retry

• /plan resume — unpauses a graph in Paused state (from Ask failure strategy), continues scheduling
• /plan retry — re-runs failed tasks in a Failed graph by resetting them to Ready

Tests (~10)

• Aggregator produces coherent output from multiple task results
• Aggregator handles graphs with skipped tasks
• Aggregator handles single-task graph
• Resume unpauses and continues scheduling
• Resume on non-paused graph returns error
• Retry resets failed tasks and re-runs
• Retry on non-failed graph returns error

Dependencies

Blocked by: Phase 4 (#1239)