perf(runtime): Hermes Phase 1-3 — prompt caching + parallel tools + smart retry

Phase 1: Anthropic prompt caching
- Add cache_control ephemeral on system prompt blocks
- Track cache_creation/cache_read tokens in CompletionResponse + StreamChunk

Phase 2A: Parallel tool execution
- Add ToolConcurrency enum (ReadOnly/Exclusive/Interactive)
- JoinSet + Semaphore(3) for bounded parallel tool calls
- 7 tools annotated with correct concurrency level
- AtomicU32 for lock-free failure tracking in ToolErrorMiddleware

Phase 2B: Tool output pruning
- prune_tool_outputs() trims old ToolResult > 2000 chars to 500 chars
- Integrated into CompactionMiddleware before token estimation

Phase 3: Error classification + smart retry
- LlmErrorKind + ClassifiedLlmError for structured error mapping
- RetryDriver decorator with jittered exponential backoff
- Kernel wraps all LLM calls with RetryDriver
- CONTEXT_OVERFLOW recovery triggers emergency compaction in loop_runner

crates/zclaw-runtime/src/driver/local.rs

@@ -238,6 +238,8 @@ impl LocalDriver {
             input_tokens,
             output_tokens,
             stop_reason,
+            cache_creation_input_tokens: None,
+            cache_read_input_tokens: None,
         }
     }
 
@@ -396,6 +398,8 @@ impl LlmDriver for LocalDriver {
                                 input_tokens: 0,
                                 output_tokens: 0,
                                 stop_reason: "end_turn".to_string(),
+                                cache_creation_input_tokens: None,
+                                cache_read_input_tokens: None,
                             });
                             continue;
                         }