fix: surface real daemon error on startup failure and hint kill PID

The CLI spawned the daemon detached with stdout/stderr redirected to
debug.log, so when the daemon exited early the user only saw a useless
'Check logs in ~/.routstrd/logs' message while the actual error sat
silently in the log file.

- daemon/index.ts: print fatal startup error to stderr (captured by the
  spawn redirect) in addition to the dated logger.
- start-daemon.ts: record debug.log offset before spawning; on early exit
  read the newly appended output and include it in the thrown error.
- coco-client.ts: add 'kill <PID>' alternative to the legacy-cocod guard
  error message alongside 'cocod stop'.

src/daemon/index.ts

@@ -335,6 +335,12 @@ async function main(): Promise<void> {
 if (import.meta.main) {
   main().catch((error) => {
     logger.error("Failed to start Routstr daemon:", error);
+    // Also write to stderr so the spawning CLI can surface the real error
+    // (stdout/stderr are redirected to debug.log by start-daemon.ts).
+    console.error(
+      "Failed to start Routstr daemon:",
+      error instanceof Error ? error.message : error,
+    );
     process.exit(1);
   });
 }

src/daemon/wallet/coco-client.ts

@@ -142,7 +142,7 @@ export async function assertLegacyCocodNotRunning(
     throw new Error(
       `Legacy cocod daemon is still running with PID ${runningPid}. ` +
         "Refusing to open the wallet database because cocod and coco-core cannot safely use it at the same time. " +
-        "Run 'cocod stop' and try again.",
+        `Run 'cocod stop' or 'kill ${runningPid}' and try again.`,
     );
   }
 
@@ -169,7 +169,7 @@ export async function assertLegacyCocodNotRunning(
       throw new Error(
         `Legacy cocod daemon is still running with PID ${newlyRunningPid}. ` +
           "Refusing to open the wallet database because cocod and coco-core cannot safely use it at the same time. " +
-          "Run 'cocod stop' and try again.",
+          `Run 'cocod stop' or 'kill ${newlyRunningPid}' and try again.`,
         { cause: error },
       );
     }

src/start-daemon.ts

@@ -1,4 +1,4 @@
-import { openSync } from "fs";
+import { openSync, existsSync, readFileSync } from "fs";
 import { logger } from "./utils/logger";
 import { CONFIG_DIR, LOGS_DIR } from "./utils/config";
 import { withCrossProcessLock } from "./utils/process-lock";
@@ -6,6 +6,27 @@ import { withCrossProcessLock } from "./utils/process-lock";
 const DAEMON_STARTUP_LOCK_PATH = `${CONFIG_DIR}/routstrd-startup.lock`;
 const DEBUG_LOG_PATH = `${CONFIG_DIR}/debug.log`;
 
+/**
+ * The spawned daemon's stdout/stderr is redirected to DEBUG_LOG_PATH, so when
+ * it exits early we can surface its actual error from there instead of just
+ * telling the user to go read logs.
+ */
+function readDaemonOutput(offset: number): string {
+  try {
+    if (!existsSync(DEBUG_LOG_PATH)) return "";
+    const content = readFileSync(DEBUG_LOG_PATH, "utf-8");
+    return content
+      .slice(offset)
+      .split("\n")
+      .map((line) => line.trim())
+      .filter(Boolean)
+      .slice(-30)
+      .join("\n");
+  } catch {
+    return "";
+  }
+}
+
 async function isDaemonHealthy(port: string): Promise<boolean> {
   const controller = new AbortController();
   const timeoutId = setTimeout(() => controller.abort(), 2000);
@@ -44,6 +65,9 @@ async function startDaemonUnlocked(
   const daemonScript = new URL("./daemon/index.js", import.meta.url).pathname;
   const shellCmd = `bun run "${daemonScript}" ${args.map((a) => `'${a}'`).join(" ")}`;
 
+  const debugLogOffset = existsSync(DEBUG_LOG_PATH)
+    ? readFileSync(DEBUG_LOG_PATH, "utf-8").length
+    : 0;
   const debugLogFd = openSync(DEBUG_LOG_PATH, "a");
 
   const proc = Bun.spawn(["sh", "-c", shellCmd], {
@@ -65,8 +89,12 @@ async function startDaemonUnlocked(
     await new Promise((resolve) => setTimeout(resolve, pollIntervalMs));
 
     if (exitCode !== null) {
+      const daemonOutput = readDaemonOutput(debugLogOffset);
       throw new Error(
-        `Daemon process exited early with code ${exitCode}. Check logs in ${LOGS_DIR}`,
+        `Daemon process exited early with code ${exitCode}.` +
+          (daemonOutput
+            ? `\n\nDaemon output:\n${daemonOutput}`
+            : ` Check logs in ${LOGS_DIR}`),
       );
     }