fix: v2.5.9 — Vietnamese in the terminal on macOS, every slash command, the right Claude account

Issue #62: a tmux client whose LC_ALL/LC_CTYPE/LANG names no UTF-8 prints `_`
for every non-ASCII character, and a macOS LaunchAgent starts the dashboard
with no locale at all — Vietnamese text and Claude Code's logo came out as
underscores in every browser terminal.

- shell-path.js: ensureUtf8Locale() defaults LC_CTYPE (en_US.UTF-8 on macOS,
  C.UTF-8 elsewhere) at start, before any tmux call; an explicit LC_ALL and
  Windows are left alone
- RunSetup.tsx: the `/` list now offers Claude Code's bundled skills
  (/code-review, /security-review, /simplify, /loop…) and newer built-ins, and
  every enabled plugin's commands and skills as /<plugin>:<name>
- Claude login decided by the TOKEN's owner (GET /api/oauth/profile, cached
  per token), not by .claude.json: a running session can leave the
  credentials store holding one account's token under another account's
  name. The Profiles modal, its Check quota and the status-bar quota now show
  the account requests are really billed to and warn on the mismatch; a
  switch saves the outgoing token into its OWNER's profile (credentials only)
  instead of overwriting the profile .claude.json names; saving a profile
  while they disagree is refused (EMISMATCH); a saved profile holding another
  account's token reports EWRONGACCOUNT instead of that account's usage
- Running Claude Code sessions follow a switch on their own (they re-read the
  credentials store when it changes), so the "close your sessions first"
  warning is gone

client/src/i18n/locales/en/ccConfig.json

@@ -263,7 +263,8 @@
     "title": "Claude Code profiles",
     "openButton": "Switch profile",
     "subtitle": "A profile is one Anthropic account - its own quota. Switching swaps only the login (credentials + account identity); skills, subagents, memory, plugins, marketplaces, MCP servers and settings all stay exactly as they are.",
-    "warning": "Close your running Claude Code sessions before switching - a live session rewrites the config on exit and would put the old account back.",
+    "warning": "Running Claude Code sessions follow a switch on their own: they pick up the new login within about 30 seconds.",
+    "mismatch": "The login in use belongs to {{owner}}, but Claude Code's config names {{config}}. Requests are billed to {{owner}}. Switch to the account you want to fix this.",
     "activeLabel": "Logged in now",
     "noActive": "No Claude account is logged in on this machine.",
     "unsavedActive": "This account is not saved as a profile yet - save it, otherwise you cannot switch away without losing its credentials.",

client/src/i18n/locales/en/nav.json

@@ -79,6 +79,7 @@
     "quotaRefreshing": "Refreshing…",
     "quotaExpired": "Token expired: use Claude Code once so it refreshes",
     "quotaFailed": "Could not read the quota",
+    "quotaWrongAccount": "This sign-in belongs to another Claude account: log in as this account and save it again",
     "quotaActive": "in use",
     "quotaProfileExpired": "Sign-in expired: use Check quota in Claude Code → Profiles to refresh it",
     "quotaSignInExpires": "Sign-in expires in {{time}}",