getStats() is noexcept but calls a WALManager query that iterates the
WAL directory, so an inaccessible directory terminated the daemon
instead of degrading to zeroed metrics. Catch and report zeros.
WALManager::getStats() also read lastSync/lastRotation after releasing
stateMutex while the sync and rotation paths write them under it. Read
them inside the same critical section.
Signed-off-by: trvon <me@trevon.dev>
WalMetricsProvider::getStats() was wired (attachWalManager) but never
consumed anywhere: WAL active/pending/total entries, bytes, and log-file
count were invisible to operators. Close the optics gap:
- MetricsSnapshot: add walActiveTransactions/PendingEntries/TotalEntries/
TotalBytes/LogFileCount (detailed snapshot only).
- DaemonMetrics::enrichDetailedSnapshot: populate from
ServiceManager::getWalMetricsProvider() (cheap atomic reads).
- request_dispatcher_status: emit wal_* requestCounts on detailed status.
- metric_keys.h: kWAL* keys (wal_active_transactions, ...).
- status_command --json: render a 'wal' object when counters are nonzero.
- tests: WalMetricsProvider pass-through unit tests (zeros without a
manager; forwards WALManager stats; reset on null manager).
Validated: build/debug suite (ConfigResolver 42 cases, metrics core/status,
new WAL provider tests) plus brick (0 new cycles on touched files) and fold
(0 findings on added lines).
