fix(electrobun): 7 bug fixes + 3 partial features completed

Bugs fixed:
- Agent retry: clear dead session on failed start (was non-recoverable)
- seqId persist: save seq_id column in agent_messages, migrate existing DBs
- Window frame save: wire resize event listener to saveWindowFrame()
- Diagnostics counters: real RPC call counter via withRpcCounting() proxy

Partial features completed:
- Search auto-seed: rebuildIndex() on startup + indexMessage() on save
- Notifications: removed 3 hardcoded demo entries, start empty
- Agent cost streaming: emitCostIfChanged() on every message batch

New: src/bun/rpc-stats.ts (RPC call + dropped event counters)

ui-electrobun/src/bun/handlers/agent-handlers.ts

@@ -4,11 +4,13 @@
 
 import type { SidecarManager } from "../sidecar-manager.ts";
 import type { SessionDb } from "../session-db.ts";
+import type { SearchDb } from "../search-db.ts";
 
 export function createAgentHandlers(
   sidecarManager: SidecarManager,
   sessionDb: SessionDb,
   sendToWebview: { send: Record<string, (...args: unknown[]) => void> },
+  searchDb?: SearchDb,
 ) {
   return {
     "agent.start": ({ sessionId, provider, prompt, cwd, model, systemPrompt, maxTurns, permissionMode, claudeConfigDir, extraEnv, additionalDirectories, worktreeName }: Record<string, unknown>) => {
@@ -21,12 +23,38 @@ export function createAgentHandlers(
         );
 
         if (result.ok) {
+          // Partial 3: Track last-sent cost to emit live updates only on change
+          let lastCostUsd = 0;
+          let lastInputTokens = 0;
+          let lastOutputTokens = 0;
+
+          /** Emit agent.cost if cost data changed since last emit. */
+          function emitCostIfChanged(sid: string): void {
+            const sessions = sidecarManager.listSessions();
+            const session = sessions.find((s: Record<string, unknown>) => s.sessionId === sid);
+            if (!session) return;
+            const cost = (session.costUsd as number) ?? 0;
+            const inTok = (session.inputTokens as number) ?? 0;
+            const outTok = (session.outputTokens as number) ?? 0;
+            if (cost === lastCostUsd && inTok === lastInputTokens && outTok === lastOutputTokens) return;
+            lastCostUsd = cost;
+            lastInputTokens = inTok;
+            lastOutputTokens = outTok;
+            try {
+              (sendToWebview.send as Record<string, Function>)["agent.cost"]({
+                sessionId: sid, costUsd: cost, inputTokens: inTok, outputTokens: outTok,
+              });
+            } catch { /* ignore */ }
+          }
+
           sidecarManager.onMessage(sessionId as string, (sid: string, messages: unknown) => {
             try {
               (sendToWebview.send as Record<string, Function>)["agent.message"]({ sessionId: sid, messages });
             } catch (err) {
               console.error("[agent.message] forward error:", err);
             }
+            // Partial 3: Stream cost on every message batch
+            emitCostIfChanged(sid);
           });
 
           sidecarManager.onStatus(sessionId as string, (sid: string, status: string, error?: string) => {
@@ -35,19 +63,7 @@ export function createAgentHandlers(
             } catch (err) {
               console.error("[agent.status] forward error:", err);
             }
-
-            const sessions = sidecarManager.listSessions();
-            const session = sessions.find((s: Record<string, unknown>) => s.sessionId === sid);
-            if (session) {
-              try {
-                (sendToWebview.send as Record<string, Function>)["agent.cost"]({
-                  sessionId: sid,
-                  costUsd: session.costUsd,
-                  inputTokens: session.inputTokens,
-                  outputTokens: session.outputTokens,
-                });
-              } catch { /* ignore */ }
-            }
+            emitCostIfChanged(sid);
           });
         }
 
@@ -122,9 +138,22 @@ export function createAgentHandlers(
         sessionDb.saveMessages(messages.map((m) => ({
           sessionId: m.sessionId, msgId: m.msgId, role: m.role,
           content: m.content, toolName: m.toolName, toolInput: m.toolInput,
-          timestamp: m.timestamp, costUsd: (m.costUsd as number) ?? 0,
+          timestamp: m.timestamp, seqId: (m.seqId as number) ?? 0,
+          costUsd: (m.costUsd as number) ?? 0,
           inputTokens: (m.inputTokens as number) ?? 0, outputTokens: (m.outputTokens as number) ?? 0,
         })));
+        // Partial 1: Index each new message in FTS5 search
+        if (searchDb) {
+          for (const m of messages) {
+            try {
+              searchDb.indexMessage(
+                String(m.sessionId ?? ""),
+                String(m.role ?? ""),
+                String(m.content ?? ""),
+              );
+            } catch { /* non-critical — don't fail the save */ }
+          }
+        }
         return { ok: true };
       } catch (err) {
         console.error("[session.messages.save]", err);