Phase 4: Atomic operations and stress testing (bd-114, bd-110)

Completes daemon architecture implementation:

Features:
- Batch/transaction API (OpBatch) for multi-step atomic operations
- Request timeout and cancellation support (30s default, configurable)
- Comprehensive stress tests (4-10 concurrent agents, 800-1000 ops)
- Performance benchmarks (daemon 2x faster than direct mode)

Results:
- Zero ID collisions across 1000+ concurrent creates
- All acceptance criteria validated for bd-110
- Create: 2.4ms (daemon) vs 4.7ms (direct)
- Update/List: similar 2x improvement

Tests Added:
- TestStressConcurrentAgents (8 agents, 800 creates)
- TestStressBatchOperations (4 agents, 400 batch ops)
- TestStressMixedOperations (6 agents, mixed read/write)
- TestStressNoUniqueConstraintViolations (10 agents, 1000 creates)
- BenchmarkDaemonCreate/Update/List/Latency
- Fixed flaky TestConcurrentRequests (shared client issue)

Files:
- internal/rpc/protocol.go - Added OpBatch, BatchArgs, BatchResponse
- internal/rpc/server.go - Implemented handleBatch with stop-on-failure
- internal/rpc/client.go - Added SetTimeout and Batch methods
- internal/rpc/stress_test.go - All stress tests
- internal/rpc/bench_test.go - Performance benchmarks
- DAEMON_STRESS_TEST.md - Complete documentation

Closes bd-114, bd-110

Amp-Thread-ID: https://ampcode.com/threads/T-1c07c140-0420-49fe-add1-b0b83b1bdff5
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/protocol.go

@@ -4,19 +4,20 @@ import "encoding/json"
 
 // Operation constants for all bd commands
 const (
-	OpPing      = "ping"
-	OpCreate    = "create"
-	OpUpdate    = "update"
-	OpClose     = "close"
-	OpList      = "list"
-	OpShow      = "show"
-	OpReady     = "ready"
-	OpStats     = "stats"
-	OpDepAdd    = "dep_add"
-	OpDepRemove = "dep_remove"
-	OpDepTree   = "dep_tree"
-	OpLabelAdd  = "label_add"
+	OpPing        = "ping"
+	OpCreate      = "create"
+	OpUpdate      = "update"
+	OpClose       = "close"
+	OpList        = "list"
+	OpShow        = "show"
+	OpReady       = "ready"
+	OpStats       = "stats"
+	OpDepAdd      = "dep_add"
+	OpDepRemove   = "dep_remove"
+	OpDepTree     = "dep_tree"
+	OpLabelAdd    = "label_add"
 	OpLabelRemove = "label_remove"
+	OpBatch       = "batch"
 )
 
 // Request represents an RPC request from client to daemon
@@ -126,3 +127,26 @@ type PingResponse struct {
 	Message string `json:"message"`
 	Version string `json:"version"`
 }
+
+// BatchArgs represents arguments for batch operations
+type BatchArgs struct {
+	Operations []BatchOperation `json:"operations"`
+}
+
+// BatchOperation represents a single operation in a batch
+type BatchOperation struct {
+	Operation string          `json:"operation"`
+	Args      json.RawMessage `json:"args"`
+}
+
+// BatchResponse contains the results of a batch operation
+type BatchResponse struct {
+	Results []BatchResult `json:"results"`
+}
+
+// BatchResult represents the result of a single operation in a batch
+type BatchResult struct {
+	Success bool            `json:"success"`
+	Data    json.RawMessage `json:"data,omitempty"`
+	Error   string          `json:"error,omitempty"`
+}