remove tmux as a required tool (dead since D-77)

Nothing has spawned tmux since D-77 moved Claude session persistence to
`--resume`; Claude and terminal panes spawn `claude` or the shell directly.
But the toolchain still resolved tmux and listed it in `missing`, so on
mac/linux a box without tmux showed a spurious "tmux not found" warning in
the welcome view + status bar. The windows-support branch had special-cased
that away with a `!Platform.isWindows` guard — the tell that the requirement
was dead everywhere, not platform-specific.

Drop tmux from ResolvedPaths / ToolchainView / Toolchain (field, getter,
`missing`, PATH resolution) on every platform, removing the Windows guards
with it. Strip the testmode tmux probes and the comments / CLAUDE.md line
that claimed clide spawns tmux. (The dead ToolCheck class that also gated on
tmux was already deleted on main and dropped in the preceding merge.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/kernel/src/toolchain.dart

@@ -21,7 +21,6 @@ export 'toolchain_paths.dart';
 class Toolchain extends ChangeNotifier implements ToolchainView {
   String? _git;
   String? _pql;
-  String? _tmux;
   String? _shell;
   Map<String, String>? _gitEnv;
   bool _resolved = false;
@@ -31,8 +30,6 @@ class Toolchain extends ChangeNotifier implements ToolchainView {
   @override
   String get pql => _pql ?? 'pql';
   @override
-  String get tmux => _tmux ?? 'tmux';
-  @override
   String get shell => _shell ?? (Platform.isWindows ? 'powershell.exe' : '/bin/bash');
 
   /// Extra environment variables for git (e.g. GIT_EXEC_PATH for dugite).
@@ -45,13 +42,7 @@ class Toolchain extends ChangeNotifier implements ToolchainView {
   bool get allOk => _resolved && missing.isEmpty;
 
   @override
-  List<String> get missing => [
-    if (_git == null) 'git',
-    if (_pql == null) 'pql',
-    // tmux has no Windows build; its absence there is the documented
-    // no-tmux mode, not a missing tool.
-    if (_tmux == null && !Platform.isWindows) 'tmux',
-  ];
+  List<String> get missing => [if (_git == null) 'git', if (_pql == null) 'pql'];
 
   /// Returns a Future that completes when resolution finishes.
   Future<void> waitForResolution() {
@@ -72,7 +63,6 @@ class Toolchain extends ChangeNotifier implements ToolchainView {
   void applyResolved(ResolvedPaths p) {
     _git = p.git;
     _pql = p.pql;
-    _tmux = p.tmux;
     _shell = p.shell;
     _gitEnv = p.gitEnv;
     _resolved = true;

lib/kernel/src/toolchain_paths.dart

@@ -12,11 +12,10 @@ import 'dart:io';
 
 /// Serializable result of tool resolution (crosses isolate boundary).
 class ResolvedPaths {
-  const ResolvedPaths({this.git, this.pql, this.tmux, this.shell, this.gitEnv});
+  const ResolvedPaths({this.git, this.pql, this.shell, this.gitEnv});
 
   final String? git;
   final String? pql;
-  final String? tmux;
   final String? shell;
   final Map<String, String>? gitEnv;
 }
@@ -32,7 +31,6 @@ abstract class ToolchainView {
 
   String get git;
   String get pql;
-  String get tmux;
   String get shell;
   Map<String, String>? get gitEnv;
   bool get resolved;
@@ -50,8 +48,6 @@ class _StaticToolchain implements ToolchainView {
   @override
   String get pql => _paths.pql ?? 'pql';
   @override
-  String get tmux => _paths.tmux ?? 'tmux';
-  @override
   String get shell => _paths.shell ?? (Platform.isWindows ? 'powershell.exe' : '/bin/bash');
   @override
   Map<String, String>? get gitEnv => _paths.gitEnv;
@@ -60,13 +56,7 @@ class _StaticToolchain implements ToolchainView {
   @override
   bool get allOk => missing.isEmpty;
   @override
-  List<String> get missing => [
-    if (_paths.git == null) 'git',
-    if (_paths.pql == null) 'pql',
-    // tmux has no Windows build; its absence there is the documented
-    // no-tmux mode, not a missing tool.
-    if (_paths.tmux == null && !Platform.isWindows) 'tmux',
-  ];
+  List<String> get missing => [if (_paths.git == null) 'git', if (_paths.pql == null) 'pql'];
 }
 
 /// Top-level function for compute/isolate use. Returns a plain-data
@@ -89,7 +79,7 @@ ResolvedPaths resolveToolchainPaths() {
     git = _findOnPath('git');
   }
 
-  return ResolvedPaths(git: git, pql: _findOnPath('pql'), tmux: _findOnPath('tmux'), shell: _resolveShell(), gitEnv: gitEnv);
+  return ResolvedPaths(git: git, pql: _findOnPath('pql'), shell: _resolveShell(), gitEnv: gitEnv);
 }
 
 /// The user's interactive shell. POSIX honours `$SHELL`; Windows has

lib/src/pty/env.dart

@@ -41,7 +41,7 @@ const Map<String, String> clidePtyEnvDefaults = {
   'COLORTERM': 'truecolor',
   // Encourages 24-bit emission from tooling that checks this:
   'CLICOLOR_FORCE': '1',
-  // tmux inherits these when clide spawns tmux; safe to propagate.
+  // UTF-8 locale for the child and anything it spawns; safe to propagate.
   'LANG': 'en_US.UTF-8',
   'LC_ALL': 'en_US.UTF-8',
 };

lib/src/pty/pty.dart

@@ -1,7 +1,7 @@
 /// PTY subsystem — spawn child processes under a PTY and expose their
 /// output as a byte stream. POSIX uses posix_openpt() + posix_spawn();
 /// Windows uses ConPTY. Desktop IDE's pane model (terminal / Claude /
-/// future tmux wrappers) rides on this.
+/// future PTY-backed panes) rides on this.
 library;
 
 export 'env.dart' show clidePtyEnvDefaults, mergePtyEnv;

lib/test_app.dart

@@ -113,22 +113,17 @@ class _ClideTestAppState extends State<ClideTestApp> {
     _say('--- toolchain ---');
     _log('toolchain.git', tc.git);
     _log('toolchain.pql', tc.pql);
-    _log('toolchain.tmux', tc.tmux);
     _log('toolchain.shell', tc.shell);
     _log('toolchain.missing', tc.missing.isEmpty ? 'none' : tc.missing.join(', '));
     _say('');
 
     await _testExists('git', tc.git);
     await _testExists('pql', tc.pql);
-    // tmux has no Windows build — its absence there is the documented
-    // no-tmux mode, so the probes would only report a non-failure.
-    if (!Platform.isWindows) await _testExists('tmux', tc.tmux);
     await _testExists('shell', tc.shell);
     _say('');
 
     await _testExec('git --version', tc.git, ['--version'], workDir);
     await _testExec('pql --version', tc.pql, ['--version'], workDir);
-    if (!Platform.isWindows) await _testExec('tmux -V', tc.tmux, ['-V'], workDir);
     // PowerShell has no --version flag; ask for the version variable
     // through the same -c path the passthrough tests use.
     await _testExec('shell --version', tc.shell, Platform.isWindows ? ['-c', r'$PSVersionTable.PSVersion.ToString()'] : ['--version'], workDir);
@@ -141,7 +136,6 @@ class _ClideTestAppState extends State<ClideTestApp> {
     String shellCall(String exe, String args) => Platform.isWindows ? "& '$exe' $args" : '$exe $args';
     await _testExec('shell -c git', tc.shell, ['-c', shellCall(tc.git, '--version')], workDir);
     await _testExec('shell -c pql', tc.shell, ['-c', shellCall(tc.pql, '--version')], workDir);
-    if (!Platform.isWindows) await _testExec('shell -c tmux', tc.shell, ['-c', shellCall(tc.tmux, '-V')], workDir);
     await _testExec('shell -c git (bare)', tc.shell, ['-c', 'git --version'], workDir);
     _say('');
 

lib/widgets/src/multitab_pane.dart

@@ -16,7 +16,7 @@ typedef MultitabEntryCallback<T> = void Function(MultitabEntry<T> entry);
 ///
 /// The widget is generic and domain-free: it never knows what's
 /// inside a tab. Hosts pick `T` and decide what add / close mean
-/// (e.g. spawning or killing a tmux session for the Claude pane).
+/// (e.g. spawning or killing a Claude session for the Claude pane).
 ///
 /// See `docs/design/multitab-pane.md` for the design rationale.
 class MultitabPane<T> extends StatelessWidget {