feat(sync): wire up sync.mode config to change sync behavior

Implements hq-ew1mbr.27: The sync.mode config now actually changes how
bd sync operates:

- git-portable (default): JSONL exported on push, imported on pull
- realtime: JSONL exported on every change (placeholder for daemon hook)
- dolt-native: Uses Dolt Push/Pull, skips JSONL workflow entirely
- belt-and-suspenders: Both Dolt remotes AND JSONL for redundancy

Changes:
- Add sync_mode.go with mode constants, Get/Set functions, and helpers
- Update bd sync --status to show actual mode from config
- Add --set-mode flag to bd sync for configuring the mode
- Modify doExportSync to respect mode (Dolt push for dolt-native)
- Modify doPullFirstSync to use Dolt pull for dolt-native mode
- Add RemoteStorage interface for Push/Pull operations
- Add comprehensive tests for sync mode functionality

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/config/sync.go

@@ -1,140 +0,0 @@
-package config
-
-import (
-	"fmt"
-	"os"
-	"strings"
-)
-
-// Sync mode configuration values (from hq-ew1mbr.3)
-// These control how Dolt syncs with JSONL/remotes.
-
-// SyncMode represents the sync mode configuration
-type SyncMode string
-
-const (
-	// SyncModeGitPortable exports JSONL on push, imports on pull (default)
-	SyncModeGitPortable SyncMode = "git-portable"
-	// SyncModeRealtime exports JSONL on every change (legacy behavior)
-	SyncModeRealtime SyncMode = "realtime"
-	// SyncModeDoltNative uses Dolt remote directly (dolthub://, gs://, s3://)
-	SyncModeDoltNative SyncMode = "dolt-native"
-	// SyncModeBeltAndSuspenders uses Dolt remote + JSONL backup
-	SyncModeBeltAndSuspenders SyncMode = "belt-and-suspenders"
-)
-
-// validSyncModes is the set of allowed sync mode values
-var validSyncModes = map[SyncMode]bool{
-	SyncModeGitPortable:       true,
-	SyncModeRealtime:          true,
-	SyncModeDoltNative:        true,
-	SyncModeBeltAndSuspenders: true,
-}
-
-// ConflictStrategy represents the conflict resolution strategy
-type ConflictStrategy string
-
-const (
-	// ConflictStrategyNewest uses last-write-wins (default)
-	ConflictStrategyNewest ConflictStrategy = "newest"
-	// ConflictStrategyOurs prefers local changes
-	ConflictStrategyOurs ConflictStrategy = "ours"
-	// ConflictStrategyTheirs prefers remote changes
-	ConflictStrategyTheirs ConflictStrategy = "theirs"
-	// ConflictStrategyManual requires manual resolution
-	ConflictStrategyManual ConflictStrategy = "manual"
-)
-
-// validConflictStrategies is the set of allowed conflict strategy values
-var validConflictStrategies = map[ConflictStrategy]bool{
-	ConflictStrategyNewest: true,
-	ConflictStrategyOurs:   true,
-	ConflictStrategyTheirs: true,
-	ConflictStrategyManual: true,
-}
-
-// Sovereignty represents the federation sovereignty tier
-type Sovereignty string
-
-const (
-	// SovereigntyT1 is the most open tier (public repos)
-	SovereigntyT1 Sovereignty = "T1"
-	// SovereigntyT2 is organization-level
-	SovereigntyT2 Sovereignty = "T2"
-	// SovereigntyT3 is pseudonymous
-	SovereigntyT3 Sovereignty = "T3"
-	// SovereigntyT4 is anonymous
-	SovereigntyT4 Sovereignty = "T4"
-)
-
-// validSovereigntyTiers is the set of allowed sovereignty values
-var validSovereigntyTiers = map[Sovereignty]bool{
-	SovereigntyT1: true,
-	SovereigntyT2: true,
-	SovereigntyT3: true,
-	SovereigntyT4: true,
-}
-
-// GetSyncMode retrieves the sync mode configuration.
-// Returns the configured mode, or SyncModeGitPortable (default) if not set or invalid.
-// Logs a warning to stderr if an invalid value is configured.
-//
-// Config key: sync.mode
-// Valid values: git-portable, realtime, dolt-native, belt-and-suspenders
-func GetSyncMode() SyncMode {
-	value := GetString("sync.mode")
-	if value == "" {
-		return SyncModeGitPortable // Default
-	}
-
-	mode := SyncMode(strings.ToLower(strings.TrimSpace(value)))
-	if !validSyncModes[mode] {
-		fmt.Fprintf(os.Stderr, "Warning: invalid sync.mode %q in config (valid: git-portable, realtime, dolt-native, belt-and-suspenders), using default 'git-portable'\n", value)
-		return SyncModeGitPortable
-	}
-
-	return mode
-}
-
-// GetConflictStrategy retrieves the conflict resolution strategy configuration.
-// Returns the configured strategy, or ConflictStrategyNewest (default) if not set or invalid.
-// Logs a warning to stderr if an invalid value is configured.
-//
-// Config key: conflict.strategy
-// Valid values: newest, ours, theirs, manual
-func GetConflictStrategy() ConflictStrategy {
-	value := GetString("conflict.strategy")
-	if value == "" {
-		return ConflictStrategyNewest // Default
-	}
-
-	strategy := ConflictStrategy(strings.ToLower(strings.TrimSpace(value)))
-	if !validConflictStrategies[strategy] {
-		fmt.Fprintf(os.Stderr, "Warning: invalid conflict.strategy %q in config (valid: newest, ours, theirs, manual), using default 'newest'\n", value)
-		return ConflictStrategyNewest
-	}
-
-	return strategy
-}
-
-// GetSovereignty retrieves the federation sovereignty tier configuration.
-// Returns the configured tier, or SovereigntyT1 (default) if not set or invalid.
-// Logs a warning to stderr if an invalid value is configured.
-//
-// Config key: federation.sovereignty
-// Valid values: T1, T2, T3, T4
-func GetSovereignty() Sovereignty {
-	value := GetString("federation.sovereignty")
-	if value == "" {
-		return SovereigntyT1 // Default
-	}
-
-	// Normalize to uppercase for comparison (T1, T2, etc.)
-	tier := Sovereignty(strings.ToUpper(strings.TrimSpace(value)))
-	if !validSovereigntyTiers[tier] {
-		fmt.Fprintf(os.Stderr, "Warning: invalid federation.sovereignty %q in config (valid: T1, T2, T3, T4), using default 'T1'\n", value)
-		return SovereigntyT1
-	}
-
-	return tier
-}