Enhance benchmark pipeline with improved async handling and error detection

Refactor the benchmark pipeline to better manage async job attributes, ensuring that the item attribute is correctly accessed from the _async_job. This change improves eligible model detection by chaining the mapping of _async_job to item. Additionally, replace the single accumulate task with per-node loops to maintain the integrity of the item data before the compute task.

Update the outer batch loop in 03_benchmark.yml to include loop_var: _batch, addressing Ansible loop-variable collision warnings. Reset model_selection.json to prevent issues from previous runs.

benchmarks/results/benchmark_20260308T145246.md

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+# Benchmark Results - 20260308T145246
+
+## Model Selection (6-slot / 2-socket)
+| Slot | Socket | Role | Model | Composite Score |
+|------|--------|------|-------|----------------|
+| 1 | Node 1 (port 11434) | General (locked) | llama3.2:3b | 0.001 |
+| 2 | Node 1 (port 11434) | General (locked) | mistral-nemo:latest | 0.0 |
+| 5 | Node 1 (port 11434) | General (rotate) | mistral:latest | 0.0 |
+| 3 | Node 0 (port 11435) | Coding (locked) | qwen2.5-coder:7b | 0.0 |
+| 4 | Node 0 (port 11435) | Coding (locked) | qwen2.5-coder:7b | 0.0 |
+| 6 | Node 0 (port 11435) | Coding (rotate) | none | N/A |
+
+## Detailed Metrics
+### mistral-nemo:latest
+- **Category**: general
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.0
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.0
+- **General Composite**: 0.0
+### mistral:latest
+- **Category**: general
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.0
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.0
+- **General Composite**: 0.0
+### llama3.1:8b
+- **Category**: general
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.0
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.0
+- **General Composite**: 0.0
+### qwen2.5-coder:7b
+- **Category**: coding
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.0
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.0
+- **General Composite**: 0.0
+### gemma3:12b-it-q4_K_M
+- **Category**: general
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.0
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.0
+- **General Composite**: 0.0
+### llama3.2:3b
+- **Category**: general
+- **Coding Quality**: 0
+- **General Quality**: 0
+- **Avg Tokens/sec**: 0.1
+- **Latency (ms)**: 109301.3
+- **Coding Composite**: 0.001
+- **General Composite**: 0.001
+
+## Scoring Formula
+- Composite = quality * 0.45 + token_speed_normalized * 0.30 + latency_score * 0.25
+- Speed normalized against 40 tok/sec ceiling (hardware-observed max)
+- Coding quality (per-prompt):
+  code_gen: has_def×0.20 + has_return×0.20 + has_docstring×0.15 + has_type_hint×0.15 + has_code_block×0.10 + has_assert×0.08 + has_test_def×0.07 + has_import×0.05
+  debug:    has_def×0.30 + has_return×0.30 + has_code_block×0.25 + has_assert×0.15
+  refactor: has_def×0.25 + has_return×0.25 + has_code_block×0.20 + has_type_hint×0.15 + has_import×0.15
+- Category: override dict → quality delta (coding_avg - general_avg >= 0.1) → name pattern (coder/codestral/codellama/starcoder) → general

benchmarks/results/benchmark_20260308T215747.md

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+# Benchmark Results - 20260308T215747
+
+## Model Selection (6-slot / 2-socket)
+
+
+| Slot | Socket              | Role             | Model               | Composite Score |
+| ---- | ------------------- | ---------------- | ------------------- | --------------- |
+| 1    | Node 1 (port 11434) | General (locked) | llama3.2:3b         | 0.45            |
+| 2    | Node 1 (port 11434) | General (locked) | mistral-nemo:latest | 0.45            |
+| 5    | Node 1 (port 11434) | General (rotate) | none                | N/A             |
+| 3    | Node 0 (port 11435) | Coding (locked)  | qwen2.5-coder:7b    | 0.371           |
+| 4    | Node 0 (port 11435) | Coding (locked)  | qwen2.5-coder:7b    | 0.371           |
+| 6    | Node 0 (port 11435) | Coding (rotate)  | none                | N/A             |
+
+
+## Detailed Metrics
+
+### llama3.2:3b
+
+- **Category**: general
+- **Coding Quality**: 0.917
+- **General Quality**: 1.0
+- **Avg Tokens/sec**: 0.1
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.413
+- **General Composite**: 0.45
+
+### qwen2.5-coder:7b
+
+- **Category**: coding
+- **Coding Quality**: 0.823
+- **General Quality**: 0.85
+- **Avg Tokens/sec**: 0.1
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.371
+- **General Composite**: 0.383
+
+### mistral-nemo:latest
+
+- **Category**: general
+- **Coding Quality**: 0.85
+- **General Quality**: 1.0
+- **Avg Tokens/sec**: 0.1
+- **Latency (ms)**: 9999
+- **Coding Composite**: 0.383
+- **General Composite**: 0.45
+
+## Scoring Formula
+
+- Composite = quality * 0.45 + token_speed_normalized * 0.30 + latency_score * 0.25
+- Speed normalized against 40 tok/sec ceiling (hardware-observed max)
+- Coding quality (per-prompt):
+code_gen: has_def×0.20 + has_return×0.20 + has_docstring×0.15 + has_type_hint×0.15 + has_code_block×0.10 + has_assert×0.08 + has_test_def×0.07 + has_import×0.05
+debug:    has_def×0.30 + has_return×0.30 + has_code_block×0.25 + has_assert×0.15
+refactor: has_def×0.25 + has_return×0.25 + has_code_block×0.20 + has_type_hint×0.15 + has_import×0.15
+- Category: override dict → quality delta (coding_avg - general_avg >= 0.1) → name pattern (coder/codestral/codellama/starcoder) → general
+