refactor(sync): rename ConnectedDegraded to ConnectedHistoricSyncFailures

Resolves naming conflict with RelayHealthState::Degraded by using a more
explicit name that clearly indicates the connection status relates to
historic sync failures, not connection health degradation.

Changes:
- ConnectionStatus::ConnectedDegraded → ConnectedHistoricSyncFailures
- Updated all documentation and comments
- Updated Prometheus metric descriptions
- Metric value remains 4 for backward compatibility

This makes it clear that:
- ConnectedHistoricSyncFailures = connection lifecycle (missing historic data)
- RelayHealthState::Degraded = connection health (reliability issues)

These are orthogonal concerns - a relay can be ConnectedHistoricSyncFailures
but Healthy, or Connected but Degraded.

1 files changed, 5 insertions, 5 deletions

diff --git a/docs/explanation/monitoring.md b/docs/explanation/monitoring.md
index cc164ab..7520813 100644
--- a/docs/explanation/monitoring.md
+++ b/docs/explanation/monitoring.md
@@ -98,7 +98,7 @@ When GRASP-02 proactive sync is implemented, the following metrics will be added
 
 | Metric | Type | Labels | Description |
 |--------|------|--------|-------------|
-| `ngit_sync_relay_connected` | Gauge | relay | Connection status (0=disconnected, 1=connecting, 2=syncing, 3=connected, 4=connected_degraded) |
+| `ngit_sync_relay_connected` | Gauge | relay | Connection status (0=disconnected, 1=connecting, 2=syncing, 3=connected, 4=connected_historic_sync_failures) |
 | `ngit_sync_connection_attempts_total` | Counter | relay, result | Connection attempt outcomes |
 | `ngit_sync_relay_status` | Gauge | relay | Health status (1=healthy, 2=disconnected, 3=degraded, 4=dead, 5=rate_limited) |
 | `ngit_sync_relay_failures` | Gauge | relay | Current consecutive failure count |
@@ -115,9 +115,9 @@ The `ngit_sync_relay_connected` metric tracks the connection lifecycle:
 - `1` = **Connecting** - Connection attempt in progress
 - `2` = **Syncing** - Connected, historic sync in progress
 - `3` = **Connected** - Connected, historic sync complete, live sync active
-- `4` = **ConnectedDegraded** - Connected, historic sync failed, live sync active, partial data
+- `4` = **ConnectedHistoricSyncFailures** - Connected, historic sync had failures, live sync active, partial data
 
-This allows operators to distinguish between "connected but still catching up" (Syncing) vs "fully synced and live" (Connected) vs "degraded - missing historic data" (ConnectedDegraded).
+This allows operators to distinguish between "connected but still catching up" (Syncing) vs "fully synced and live" (Connected) vs "historic sync failures - missing historic data" (ConnectedHistoricSyncFailures).
 
 ### Relay Health States
 
@@ -137,12 +137,12 @@ sum by (relay) (ngit_sync_relay_connected == 0)  # Disconnected
 sum by (relay) (ngit_sync_relay_connected == 1)  # Connecting
 sum by (relay) (ngit_sync_relay_connected == 2)  # Syncing
 sum by (relay) (ngit_sync_relay_connected == 3)  # Connected
-sum by (relay) (ngit_sync_relay_connected == 4)  # ConnectedDegraded
+sum by (relay) (ngit_sync_relay_connected == 4)  # ConnectedHistoricSyncFailures
 
 # Relays still syncing (not yet fully caught up)
 count(ngit_sync_relay_connected == 2)
 
-# Relays with degraded sync (missing historic data)
+# Relays with historic sync failures (missing historic data)
 count(ngit_sync_relay_connected == 4)
 
 # Connection success rate over last hour