PCSM-219: Consolidate configuration documentation

- Add configuration reference table to config/config.go (single source of truth)
- Remove redundant config source comments from config/values.go
- Remove references to external decision documents
- Simplify function comments to describe behavior, not configuration

Author: chupe

config/config.go

@@ -34,8 +34,26 @@ func Init(cmd *cobra.Command) {
 }
 
 // bindEnvVars binds environment variable names to Viper keys.
-// Only global/server options have env var support.
-// Clone tuning options are intentionally NOT bound (CLI/HTTP only).
+//
+// Configuration Reference:
+//
+//	| Viper Key                      | CLI Flag                          | Env Var                              | Default |
+//	|--------------------------------|-----------------------------------|--------------------------------------|---------|
+//	| source                         | --source                          | PCSM_SOURCE_URI                      | -       |
+//	| target                         | --target                          | PCSM_TARGET_URI                      | -       |
+//	| port                           | --port                            | PCSM_PORT                            | 2242    |
+//	| log-level                      | --log-level                       | PCSM_LOG_LEVEL                       | info    |
+//	| log-json                       | --log-json                        | PCSM_LOG_JSON                        | false   |
+//	| no-color                       | --no-color                        | PCSM_NO_COLOR                        | false   |
+//	| mongodb-cli-operation-timeout  | --mongodb-cli-operation-timeout   | PCSM_MONGODB_CLI_OPERATION_TIMEOUT   | 5m      |
+//	| use-collection-bulk-write      | --use-collection-bulk-write       | PCSM_USE_COLLECTION_BULK_WRITE       | false   |
+//	| clone-num-parallel-collections | --clone-num-parallel-collections  | -                                    | 0       |
+//	| clone-num-read-workers         | --clone-num-read-workers          | -                                    | 0       |
+//	| clone-num-insert-workers       | --clone-num-insert-workers        | -                                    | 0       |
+//	| clone-segment-size             | --clone-segment-size              | -                                    | 0       |
+//	| clone-read-batch-size          | --clone-read-batch-size           | -                                    | 0       |
+//
+// Note: Clone tuning options are CLI/HTTP only (no env var support).
 func bindEnvVars() {
 	// Server connection URIs
 	_ = viper.BindEnv("source", "PCSM_SOURCE_URI")
@@ -44,12 +62,8 @@ func bindEnvVars() {
 	// MongoDB client timeout
 	_ = viper.BindEnv("mongodb-cli-operation-timeout", "PCSM_MONGODB_CLI_OPERATION_TIMEOUT")
 
-	// Bulk write option (internal, has env var support)
+	// Bulk write option (hidden, internal use)
 	_ = viper.BindEnv("use-collection-bulk-write", "PCSM_USE_COLLECTION_BULK_WRITE")
-
-	// NOTE: Clone tuning options intentionally NOT bound to env vars.
-	// They are CLI/HTTP-only per stakeholder decision (PCSM-219).
-	// See: comment-decisions.md - Decision #2
 }
 
 // GetString returns a string configuration value from Viper.

config/values.go

@@ -12,52 +12,31 @@ import (
 )
 
 // UseCollectionBulkWrite returns whether to use collection-level bulk write.
-// This is an internal option, not exposed via HTTP API.
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --use-collection-bulk-write (hidden)
-//   - Env var: PCSM_USE_COLLECTION_BULK_WRITE
-//   - Default: false
+// Internal option, not exposed via HTTP API.
 func UseCollectionBulkWrite() bool {
 	return viper.GetBool("use-collection-bulk-write")
 }
 
 // CloneNumParallelCollections returns the number of collections to clone in parallel.
-// Configurable via CLI flag only (no env var support per decision #2).
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --clone-num-parallel-collections
-//   - Default: 0 (auto)
+// Returns 0 for auto-detection.
 func CloneNumParallelCollections() int {
 	return viper.GetInt("clone-num-parallel-collections")
 }
 
 // CloneNumReadWorkers returns the number of read workers.
-// Configurable via CLI flag only (no env var support per decision #2).
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --clone-num-read-workers
-//   - Default: 0 (auto)
+// Returns 0 for auto-detection.
 func CloneNumReadWorkers() int {
 	return viper.GetInt("clone-num-read-workers")
 }
 
 // CloneNumInsertWorkers returns the number of insert workers.
-// Configurable via CLI flag only (no env var support per decision #2).
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --clone-num-insert-workers
-//   - Default: 0 (auto)
+// Returns 0 for auto-detection.
 func CloneNumInsertWorkers() int {
 	return viper.GetInt("clone-num-insert-workers")
 }
 
 // CloneSegmentSizeBytes returns the segment size in bytes.
-// Configurable via CLI flag only (no env var support per decision #2).
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --clone-segment-size
-//   - Default: AutoCloneSegmentSize (0 = auto)
+// Returns 0 (AutoCloneSegmentSize) for auto-detection.
 func CloneSegmentSizeBytes() int64 {
 	sizeStr := viper.GetString("clone-segment-size")
 	if sizeStr == "" {
@@ -73,11 +52,7 @@ func CloneSegmentSizeBytes() int64 {
 }
 
 // CloneReadBatchSizeBytes returns the read batch size in bytes.
-// Configurable via CLI flag only (no env var support per decision #2).
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --clone-read-batch-size
-//   - Default: 0 (uses MaxWriteBatchSizeBytes)
+// Returns 0 to use MaxWriteBatchSizeBytes default.
 func CloneReadBatchSizeBytes() int32 {
 	sizeStr := viper.GetString("clone-read-batch-size")
 	if sizeStr == "" {
@@ -112,11 +87,6 @@ func UseTargetClientCompressors() []string {
 }
 
 // MongoDBOperationTimeout returns the timeout for MongoDB client operations.
-//
-// Configuration sources (in order of precedence):
-//   - CLI flag: --mongodb-cli-operation-timeout
-//   - Env var: PCSM_MONGODB_CLI_OPERATION_TIMEOUT
-//   - Default: 5m
 func MongoDBOperationTimeout() time.Duration {
 	timeoutStr := viper.GetString("mongodb-cli-operation-timeout")
 	if timeoutStr != "" {