fix: switch prefix ASCII input source on the foreground client (#1016)

* fix: switch prefix ASCII input source on the foreground client

The macOS prefix ASCII-switch ran in the headless server, whose
TISCopyCurrentKeyboardInputSource read is a stale per-process cache
(refreshed only via a main-run-loop notification the server never pumps),
so prefix could leave the terminal on the wrong input source.

Forward it to the foreground client, like clipboard: sync_prefix_input_source
emits AppEvent::PrefixInputSource as an intent; the server forwards it to the
foreground client and the monolithic app applies it in-process via
RealPrefixInputSource, which pumps its main run loop before the stale TIS read.
Key it on Mode::wants_ascii_input so multi-level prefix commands keep ASCII
until returning to the terminal, and restore the IME for rename text entry.

Adds ServerMessage::PrefixInputSource to the already-unreleased protocol 15.

refs #774

* fix: keep prefix input-source switch out of the headless server process

An App-internal drain (the exhaustive drain at the top of
handle_api_request, reachable from prefix-key runtime mutations) can
consume a queued PrefixInputSource intent before the server's
forwarding drain sees it, applying the TIS switch in the headless
server process and stranding the restore state. Gate the in-process
switch on App.local_input_source_switch, disabled by the headless
server alongside the other local side effects, so a swallowed intent
degrades to a skipped switch. Widen the forwarding-bypass maintenance
test to the handle_internal_event_with_prefix_sync wrapper.

refs #774

* docs: clarify prefix input-source comments and flag docs

refs #774

* fix: bump protocol for prefix input source

refs #774

---------

Co-authored-by: Ogulcan Celik <ogulcancelik@gmail.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/app/state.rs b/src/app/state.rs
index 99ab648b..eee61566 100644
--- a/src/app/state.rs
+++ b/src/app/state.rs
@@ -768,6 +768,33 @@ pub enum Mode {
     Navigator,
 }
 
+impl Mode {
+    /// Whether keys in this mode are commands/navigation (an ASCII input source is wanted) rather
+    /// than free text. This is an explicit **allowlist** of the prefix command/navigation realm:
+    /// any mode NOT listed defaults to leaving the user's IME alone (the safe default), so adding a
+    /// new text-entry or overlay mode can never silently force ASCII. Used by
+    /// `sync_prefix_input_source` (gated by `switch_ascii_input_source_in_prefix`) so multi-level
+    /// prefix commands keep ASCII until they return to the terminal.
+    ///
+    /// Known limitation: `Navigator`'s search box is also held on ASCII, since this `Mode`-level
+    /// predicate can't see `search_focused` (non-ASCII filtering there would need a runtime check).
+    pub(crate) fn wants_ascii_input(self) -> bool {
+        matches!(
+            self,
+            Mode::Prefix
+                | Mode::Navigate
+                | Mode::Navigator
+                | Mode::Copy
+                | Mode::Resize
+                | Mode::ConfirmClose
+                | Mode::ConfirmRemoveWorktree
+                | Mode::ContextMenu
+                | Mode::GlobalMenu
+                | Mode::KeybindHelp
+        )
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub(crate) enum NavigatorTarget {
     Workspace {