fix(mode-switch): signal forwarding prevents orphaned processes (slopus#11)

## THE FIX
Forward SIGTERM, SIGINT, SIGHUP to child Claude CLI process.
This ensures child processes are killed when parent is terminated.

## ROOT CAUSE
When switching between local/remote modes, the parent process was killed
but child Claude CLI processes remained alive ("orphaned"). These orphaned
processes continued to hold stdin, causing:
- Duplicate/garbled characters when typing
- "Competing processes" fighting for terminal input

## SOLUTION (from GitHub slopus/happy#430)
```javascript
const forwardSignal = (signal) => {
    if (child.pid && !child.killed) {
        child.kill(signal);
    }
};
process.on('SIGTERM', () => forwardSignal('SIGTERM'));
process.on('SIGINT', () => forwardSignal('SIGINT'));
process.on('SIGHUP', () => forwardSignal('SIGHUP'));
```

## FILES CHANGED
- scripts/claude_version_utils.cjs - binary launcher signal forwarding
- src/claude/claudeLocal.ts - TypeScript launcher signal forwarding

## TESTED
✅ Fresh local mode - typing works
✅ Switch to remote mode - typing works
✅ Switch back to local mode - typing works (was broken)
✅ Multiple mode switches - stable

## IMPORTANT
This is the ONLY fix needed. No stdin cleanup, no removeAllListeners(),
no setRawMode changes required. Signal forwarding alone solves it.

Closes slopus#11
References: slopus/happy#430, PR slopus#127

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

package.json

@@ -1,6 +1,6 @@
 {
   "name": "happy-coder",
-  "version": "0.14.0-0",
+  "version": "0.14.1-0",
   "description": "Mobile and Web client for Claude Code and Codex",
   "author": "Kirill Dubovitskiy",
   "license": "MIT",

scripts/claude_version_utils.cjs

@@ -497,6 +497,19 @@ function runClaudeCli(cliPath) {
             stdio: 'inherit',
             env: process.env
         });
+
+        // Forward signals to child process so it gets killed when parent is killed
+        // This prevents orphaned Claude processes when switching between local/remote modes
+        // Fix for issue #11 / GitHub slopus/happy#430
+        const forwardSignal = (signal) => {
+            if (child.pid && !child.killed) {
+                child.kill(signal);
+            }
+        };
+        process.on('SIGTERM', () => forwardSignal('SIGTERM'));
+        process.on('SIGINT', () => forwardSignal('SIGINT'));
+        process.on('SIGHUP', () => forwardSignal('SIGHUP'));
+
         child.on('exit', (code) => {
             process.exit(code || 0);
         });

src/claude/claudeLocal.ts

@@ -232,6 +232,29 @@ export async function claudeLocal(opts: {
                 env,
             });
 
+            // Forward signals to child process to prevent orphaned processes
+            // Fix for issue #11 / GitHub slopus/happy#430
+            // Note: signal: opts.abort handles programmatic abort (mode switching),
+            // but direct OS signals (e.g., kill, Ctrl+C) need explicit forwarding
+            const forwardSignal = (signal: NodeJS.Signals) => {
+                if (child.pid && !child.killed) {
+                    child.kill(signal);
+                }
+            };
+            const onSigterm = () => forwardSignal('SIGTERM');
+            const onSigint = () => forwardSignal('SIGINT');
+            const onSighup = () => forwardSignal('SIGHUP');
+            process.on('SIGTERM', onSigterm);
+            process.on('SIGINT', onSigint);
+            process.on('SIGHUP', onSighup);
+
+            // Cleanup signal handlers when child exits to avoid leaks
+            child.on('exit', () => {
+                process.off('SIGTERM', onSigterm);
+                process.off('SIGINT', onSigint);
+                process.off('SIGHUP', onSighup);
+            });
+
             // Listen to the custom fd (fd 3) for thinking state tracking
             if (child.stdio[3]) {
                 const rl = createInterface({