fix(terminal): drop native ARGV0 for bun-pty via env -u

bun-pty merges the OS environ into PTY children, so deleting ARGV0 from the
JS env object alone left the AppImage path in the shell. Wrap Linux PTY
spawns with env -u ARGV0, clear native ARGV0 under Bun via libc unsetenv,
and always clear process.env even when no login-shell snapshot exists.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/web/server/lib/opencode/env-runtime.test.js

@@ -153,6 +153,21 @@ describe('OpenCode env runtime', () => {
     }
   });
 
+  it('clears AppImage ARGV0 even when no login-shell snapshot is available', () => {
+    const previousArgv0 = process.env.ARGV0;
+    process.env.ARGV0 = '/path/to/OpenChamber.AppImage';
+    const { runtime, state } = createRuntime({});
+    state.cachedLoginShellEnvSnapshot = null;
+
+    try {
+      runtime.applyLoginShellEnvSnapshot();
+      expect(process.env.ARGV0).toBeUndefined();
+    } finally {
+      if (previousArgv0 === undefined) delete process.env.ARGV0;
+      else process.env.ARGV0 = previousArgv0;
+    }
+  });
+
   it('throws a specific error for a missing configured OpenCode binary in strict mode', async () => {
     const { runtime } = createRuntime({ opencodeBinary: '/missing/opencode' });