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, 2 insertions, 2 deletions

diff --git a/docs/next/website/src/content/docs/configuration.mdx b/docs/next/website/src/content/docs/configuration.mdx
index 0305a670..b17107df 100644
--- a/docs/next/website/src/content/docs/configuration.mdx
+++ b/docs/next/website/src/content/docs/configuration.mdx
@@ -500,14 +500,14 @@ The trade-off when enabled: an extra hardware cursor is visible in the outer ter
 
 On macOS, prefix-mode commands can be hard to use while a non-ASCII input source is active because prefix commands are still interpreted through the host input source.
 
-Set `switch_ascii_input_source_in_prefix = true` to switch the host input source to the system ASCII-capable input source while prefix mode is active:
+Set `switch_ascii_input_source_in_prefix = true` to switch the host input source to the system ASCII-capable input source while prefix commands and prefix-launched navigation are active:
 
 ```toml
 [experimental]
 switch_ascii_input_source_in_prefix = false
 ```
 
-When enabled, Herdr switches input sources only after prefix mode is entered, then restores the previous input source when prefix mode exits. The setting is macOS-only and is a no-op on other platforms or when the system input-source switch fails.
+When enabled, Herdr switches input sources after prefix mode is entered, keeps the ASCII source across prefix-launched modes such as navigation, menus, resize, and copy mode, and restores the previous input source when returning to the terminal or entering a text field such as a rename dialog. The setting is macOS-only and is a no-op on other platforms or when the system input-source switch fails.
 
 You can also toggle it from Settings > Experiments > switch to ascii input source in prefix (macOS).