fix(server): fall back to a UTF-8 locale in terminal spawn env

[Kaidstor]

What Changed

The terminal manager now falls back to a UTF-8 locale when spawning a PTY whose environment defines neither LANG nor LC_ALL: en_US.UTF-8 on macOS, C.UTF-8 on Linux (the only one guaranteed to exist), nothing on Windows. An explicitly configured locale — even a non-UTF-8 one — and per-session runtime env overrides are left untouched. Two tests cover the fallback and the "explicit locale wins" case.

Why

GUI apps launched from the macOS Dock/Finder get no LANG/LC_* from launchd (Terminal.app and iTerm inject their own; the integrated terminal inherits the server process env instead). The PTY shell therefore starts in the single-byte C locale, and zsh's line editor mangles any multibyte input — typing non-ASCII text (e.g. Cyrillic) renders as raw bytes instead of characters:

❯ for�
❯ ???????<0080>??      # typing "фор…" — <0080> is the 2nd byte of UTF-8 "р"

Repro on macOS: launch the packaged app from the Dock, open the integrated terminal, run locale → LANG="", LC_CTYPE="C"; then type any non-ASCII character.

VS Code works around the same launchd behavior with terminal.integrated.detectLocale; this is the minimal equivalent.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (terminal transcript above; no app UI changed)

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Note

Low Risk
Localized change to PTY spawn environment with conservative defaults and no override when the user already set locale variables.

Overview
Fixes integrated terminals starting in the C locale when the server inherits a bare environment (e.g. macOS Dock/Finder via launchd), which broke multibyte shell input.

createTerminalSpawnEnv now runs withUtf8LocaleFallback after AppImage scrubbing: if neither LANG nor LC_ALL is set, it sets LANG to en_US.UTF-8 on macOS and C.UTF-8 on Linux; Windows is unchanged. Existing LANG / LC_ALL values (including non-UTF-8 locales) are not overridden.

Tests assert the macOS fallback and that an explicit LANG is preserved.

^{Reviewed by Cursor Bugbot for commit 83d4050. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fall back to a UTF-8 locale in terminal spawn env on non-Windows platforms

Introduces withUtf8LocaleFallback in Manager.ts to inject a LANG fallback when LC_ALL and LANG are absent from the spawn environment. On macOS the fallback is en_US.UTF-8; on other non-Windows platforms it is C.UTF-8. Windows and envs with an explicit locale are left unchanged. createTerminalSpawnEnv now accepts a platform argument and pipes the env through this fallback after stripping AppImage variables.

^{Macroscope summarized 83d4050.}

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[macroscopeapp]

Approvability

Verdict: Approved 83d4050

Straightforward bug fix that adds a UTF-8 locale fallback for terminal spawning when no locale is configured. The change is defensive, respects existing user settings, and includes test coverage for both the fallback and preservation behaviors.

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