fix: address Greptile P1 findings on PR #2302

- process-registry.ts: skip the trailing notifySlotAvailable() when
  pruneDeadEntries() removed entries — prune already wakes one waiter
  per removed SDK process, so the unconditional call double-woke and
  could let two waiters spawn in the same synchronous tick, briefly
  exceeding maxConcurrent. Only fire the safety-net notify when nothing
  was pruned.
- install.ts: persistClaudeProvider() no longer silently rewrites
  CLAUDE_MEM_CLAUDE_AUTH_METHOD to 'subscription'. When called without
  an explicit auth method, preserve the existing setting; only fall
  back to 'subscription' when none is configured. Prevents re-running
  'claude-mem install --provider claude' from wiping a user's
  configured 'api-key' or 'gateway' auth.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/npx-cli/commands/install.ts

@@ -591,10 +591,16 @@ type ClaudeApiMode = 'direct' | 'gateway';
 async function promptProvider(options: InstallOptions): Promise<ProviderId> {
   const initialProvider = (getSetting('CLAUDE_MEM_PROVIDER') as ProviderId) || 'claude';
 
-  const persistClaudeProvider = (authMethod: 'subscription' | 'api-key' | 'gateway' = 'subscription') => {
+  const persistClaudeProvider = (authMethod?: 'subscription' | 'api-key' | 'gateway') => {
+    const existingAuthMethod = getSetting('CLAUDE_MEM_CLAUDE_AUTH_METHOD') as
+      | 'subscription'
+      | 'api-key'
+      | 'gateway'
+      | undefined;
+    const resolvedAuthMethod = authMethod ?? existingAuthMethod ?? 'subscription';
     const wrote = mergeSettings({
       CLAUDE_MEM_PROVIDER: 'claude',
-      CLAUDE_MEM_CLAUDE_AUTH_METHOD: authMethod,
+      CLAUDE_MEM_CLAUDE_AUTH_METHOD: resolvedAuthMethod,
     });
     if (wrote) log.info('Saved Claude Agent SDK configuration to ~/.claude-mem/settings.json');
   };

src/supervisor/process-registry.ts

@@ -482,6 +482,7 @@ export async function waitForSlot(maxConcurrent: number): Promise<void> {
       const removed = getProcessRegistry().pruneDeadEntries();
       if (removed > 0) {
         logger.info('PROCESS', 'Pruned stale process registry entries while waiting for agent slot', { removed });
+        return;
       }
       notifySlotAvailable();
     }, SLOT_RECHECK_INTERVAL_MS);