refactor(i18n): split index.json into per-component files

Split locales/{lang}/index.json into 18 individual JSON files:
- One file per UI component (ui-message-view, ui-prompt-input, etc.)
- Grouped small dropdowns into ui-dropdowns.json
- Grouped undo-related into ui-undo.json
- Session, prompt, cli-help remain separate

Updated check-i18n.mjs to read all *.json files from locale dirs
instead of just index.json.

i18n.ts loadLocaleDir() already supports multi-file loading.

Author: xinggitxing

locales/en/cli-help.json

@@ -0,0 +1,42 @@
+{
+  "cli": {
+    "help": {
+      "title": "deepcode - Deep Code CLI",
+      "usage": "Usage:",
+      "launchTui": "  deepcode                              Launch the interactive TUI in the current directory",
+      "launchWithPrompt": "  deepcode -p <prompt>                  Launch with a pre-filled prompt",
+      "launchWithPromptLong": "  deepcode --prompt <prompt>            Same as -p",
+      "printVersion": "  deepcode --version                    Print the version",
+      "printHelp": "  deepcode --help                       Show this help",
+      "configSection": "Configuration:",
+      "userSettings": "  ~/.deepcode/settings.json    User-level API key, model, base URL",
+      "projectSettings": "  ./.deepcode/settings.json    Project-level settings",
+      "userSkills": "  ~/.agents/skills/*/SKILL.md  User-level skills",
+      "projectSkills": "  ./.agents/skills/*/SKILL.md  Project-level skills",
+      "legacySkills": "  ./.deepcode/skills/*/SKILL.md Legacy project-level skills",
+      "tuiSection": "Inside the TUI:",
+      "enterSend": "  enter            Send the prompt",
+      "shiftEnterNewline": "  shift+enter      Insert a newline",
+      "homeEnd": "  home/end         Move within the current line",
+      "altLeftRight": "  alt+left/right   Move by word",
+      "ctrlW": "  ctrl+w           Delete the previous word",
+      "ctrlV": "  ctrl+v           Paste an image from the clipboard",
+      "ctrlX": "  ctrl+x           Clear pasted images",
+      "esc": "  esc              Interrupt the current model turn",
+      "slash": "  /                Open the skills/commands menu",
+      "slashSkills": "  /skills          List available skills",
+      "slashModel": "  /model           Select model, thinking mode and effort control",
+      "slashNew": "  /new             Start a fresh conversation",
+      "slashInit": "  /init            Initialize an AGENTS.md file with instructions for LLM",
+      "slashResume": "  /resume          Pick a previous conversation to continue",
+      "slashContinue": "  /continue        Continue the active conversation, or resume one if empty",
+      "slashUndo": "  /undo            Restore code and/or conversation to a previous point",
+      "slashMcp": "  /mcp             Show MCP server status and available tools",
+      "slashRaw": "  /raw             Toggle display mode for viewing or collapsing reasoning content",
+      "slashExit": "  /exit            Quit",
+      "slashConfig": "  /config          Configure language settings",
+      "ctrlD": "  ctrl+d twice     Quit",
+      "ttyRequired": "deepcode requires an interactive terminal (TTY). Re-run from a real terminal session."
+    }
+  }
+}

locales/en/index.json

@@ -0,0 +1,8 @@
+{
+  "prompt": {
+    "skillDocumentsHeader": "Use the skill documents below to assist the user:\n",
+    "dateAndModel": "Today is {date}. As the conversation progresses, time passes.\nCurrent LLM model is {model}. You can switch models using the /model command.",
+    "thinkingLanguageInstruction": "IMPORTANT: Your reasoning and thinking process should be in English.",
+    "replyLanguageInstruction": "IMPORTANT: Always respond to the user in English."
+  }
+}

locales/en/prompt.json

@@ -0,0 +1,6 @@
+{
+  "session": {
+    "compacting": "The conversation is getting long, compacting...",
+    "skillPromptHeader": "Use the skill document below to assist the user:\n"
+  }
+}

locales/en/session.json

@@ -0,0 +1,23 @@
+{
+  "ui": {
+    "app": {
+      "error": "Error: {message}",
+      "statusStatus": "status: {status}",
+      "statusTokens": "tokens: {tokens}",
+      "statusFail": "fail: {reason}",
+      "interrupted": "Interrupted.",
+      "killedProcesses": "Killed processes: {pids}",
+      "failedKillProcesses": "Failed to kill processes: {pids}",
+      "modelUnchanged": "Model settings unchanged",
+      "modelUpdated": "Model settings updated: {before} → {after}",
+      "noActiveSession": "No active session to undo.",
+      "codeRestoreFailed": "Code restore failed: {error}",
+      "conversationRestoreFailed": "Conversation restore failed: {error}",
+      "sessionAgentSteps": "The AI agent has taken several steps but hasn't reached a conclusion yet. Do you want to continue?",
+      "apiKeyNotFound": "OpenAI API key not found. Please configure ~/.deepcode/settings.json or ./.deepcode/settings.json.",
+      "requestFailed": "Request failed: {error}",
+      "pressEscExitRaw": "Press ESC to exit raw mode",
+      "noMessagesInSession": "(No messages in this session yet. Start chatting to see them here.)"
+    }
+  }
+}

locales/en/ui-app.json

@@ -0,0 +1,12 @@
+{
+  "ui": {
+    "askUserQuestion": {
+      "selectOptionHelp": "Select an option, or type an Other answer.",
+      "selectMultiHelp": "Select at least one option with Space, or type an Other answer.",
+      "typeAnswerHelp": "Type your answer · Backspace edit · Enter submit/next · ↑ choose presets · Esc type manually",
+      "otherLabel": "Other",
+      "selectMultiMove": "↑/↓ move · Space toggle · Enter submit/next · Esc type manually",
+      "selectSingleMove": "↑/↓ move · Enter select/next · Esc type manually"
+    }
+  }
+}