refactor: remove client-side session ID management

Remove proactive session ID generation and onSessionFound callback. Let Claude
handle session creation automatically via the SessionStart hook instead. This
simplifies the API contract and delegates session lifecycle management to Claude.

cli/src/claude/claudeLocal.ts

@@ -1,6 +1,5 @@
 import { spawn } from "node:child_process";
 import { mkdirSync } from "node:fs";
-import { randomUUID } from "node:crypto";
 import { logger } from "@/ui/logger";
 import { claudeCheckSession } from "./utils/claudeCheckSession";
 import { getProjectPath } from "./utils/path";
@@ -12,7 +11,6 @@ export async function claudeLocal(opts: {
     sessionId: string | null,
     mcpServers?: Record<string, any>,
     path: string,
-    onSessionFound: (id: string) => void,
     claudeEnvVars?: Record<string, string>,
     claudeArgs?: string[]
     allowedTools?: string[]
@@ -23,27 +21,19 @@ export async function claudeLocal(opts: {
     const projectDir = getProjectPath(opts.path);
     mkdirSync(projectDir, { recursive: true });
 
-    // Determine session ID strategy:
-    // - If resuming an existing session: use --resume (Claude keeps the same session ID)
-    // - If starting fresh: generate UUID and pass via --session-id
+    // Check if user passed explicit session control flags.
+    const hasContinueFlag = opts.claudeArgs?.includes('--continue');
+    const hasResumeFlag = opts.claudeArgs?.includes('--resume');
+    const hasUserSessionControl = Boolean(hasContinueFlag || hasResumeFlag);
+
+    // Determine session strategy:
+    // - If resuming an existing session: use --resume (unless user already supplied session control)
+    // - If starting fresh: let Claude create a new session ID (reported via SessionStart hook)
     let startFrom = opts.sessionId;
     if (opts.sessionId && !claudeCheckSession(opts.sessionId, opts.path)) {
         startFrom = null;
     }
 
-    // Generate new session ID if not resuming
-    const newSessionId = startFrom ? null : randomUUID();
-    const effectiveSessionId = startFrom || newSessionId!;
-    
-    // Notify about session ID immediately (we know it upfront now!)
-    if (newSessionId) {
-        logger.debug(`[ClaudeLocal] Generated new session ID: ${newSessionId}`);
-        opts.onSessionFound(newSessionId);
-    } else {
-        logger.debug(`[ClaudeLocal] Resuming session: ${startFrom}`);
-        opts.onSessionFound(startFrom!);
-    }
-
     // Spawn the process
     try {
         // Start the interactive process
@@ -51,12 +41,9 @@ export async function claudeLocal(opts: {
         await new Promise<void>((r, reject) => {
             const args: string[] = []
             
-            if (startFrom) {
-                // Resume existing session (Claude preserves the session ID)
+            if (startFrom && !hasUserSessionControl) {
+                // Resume existing session
                 args.push('--resume', startFrom)
-            } else {
-                // New session with our generated UUID
-                args.push('--session-id', newSessionId!)
             }
             
             args.push('--append-system-prompt', systemPrompt);
@@ -79,7 +66,7 @@ export async function claudeLocal(opts: {
             logger.debug(`[ClaudeLocal] Using hook settings: ${opts.hookSettingsPath}`);
 
             // Prepare environment variables
-            // Note: Local mode uses global Claude installation with --session-id flag
+            // Note: Local mode uses global Claude installation
             const env = {
                 ...process.env,
                 DISABLE_AUTOUPDATER: '1',
@@ -127,5 +114,5 @@ export async function claudeLocal(opts: {
         process.stdin.resume();
     }
 
-    return effectiveSessionId;
+    return startFrom ?? null;
 }

cli/src/claude/claudeLocalLauncher.ts

@@ -80,11 +80,6 @@ export async function claudeLocalLauncher(session: Session): Promise<'switch' |
             return 'switch';
         }
 
-        // Handle session start
-        const handleSessionStart = (sessionId: string) => {
-            session.onSessionFound(sessionId);
-        }
-
         // Run local mode
         while (true) {
             // If we already have an exit reason, return it
@@ -98,7 +93,6 @@ export async function claudeLocalLauncher(session: Session): Promise<'switch' |
                 await claudeLocal({
                     path: session.path,
                     sessionId: session.sessionId,
-                    onSessionFound: handleSessionStart,
                     abort: processAbortController.signal,
                     claudeEnvVars: session.claudeEnvVars,
                     claudeArgs: session.claudeArgs,