feat: cursor navigation, key sounds, dictionary tooling, key security

Batch of in-progress app work from the working tree.

- feat(keyboard): CursorNavigation + CursorDragPad for caret movement;
  KeyboardSoundFeedback for system key click sounds
- feat(dictionary): DictionaryAliasGenerator + PersonalDictionaryEntrySheet;
  TranscriptPostProcessor quality gate; retire DictionaryLearner
- feat(ui): TabBarVisibility handling; drop PageHeaderRow /
  PageHeaderConfirmButton; refresh views and localizable strings
- fix(security): move the hardcoded DeepSeek key out of
  PreconfiguredKeys.swift into a gitignored PreconfiguredKeys.local.swift
  (seeded from .example by generate-xcodeproj.sh)
- docs(agents): add Conventional Commits versioning + bilingual changelog rules
- chore(gitignore): ignore PreconfiguredKeys.local.swift, .cache/, pycache

Custom language model / lexicon work stays on
feature/custom-language-model-asr. Changelog bullets added under
[Unreleased]; no version bump.

OSGKeyboardExt/en.lproj/Keyboard.strings

@@ -128,6 +128,8 @@
 "keyboard.openSettingsA11y" = "Open OSGKeyboard settings";
 "keyboard.deniedHint" = "Opens the OSGKeyboard settings page where you can grant microphone or speech recognition access.";
 "keyboard.tapToTalkA11y" = "Tap to talk";
+"keyboard.cursorDrag.hint" = "Hold and drag to move the cursor";
+"keyboard.cursorDrag.centerHint" = "Drag to move the cursor";
 
 /* Flow session (keyboard) */
 "keyboard.flow.sessionInactive" = "Voice session off";
@@ -155,6 +157,8 @@
 "keyboard.error.manualOpenDictateLocal" = "System blocked the jump. Open OSGKeyboard for on-device dictation, then return.";
 "keyboard.error.manualOpenDictate" = "System blocked the jump. Open OSGKeyboard to record, then return.";
 "keyboard.error.llm.noApiKey" = "API key missing · configure it in the main app";
+"keyboard.mic.disabled.missingApiKey" = "Fill in API key in Settings first";
+"keyboard.error.llm.localPolishUnavailable" = "Built-in polish unavailable · inserted raw text";
 "keyboard.error.llm.unauthorized" = "Invalid API key (401) · check main app settings";
 "keyboard.error.llm.rateLimited" = "Rate limited (429) · try again later";
 
@@ -234,6 +238,6 @@
 "keyboard.appContext.chip.unknown"  = "General";
 "keyboard.appContext.menu.code"     = "Code — preserve identifiers, no natural-language wrap";
 "keyboard.appContext.menu.email"    = "Email — polite, professional, paragraph-broken";
-"keyboard.appContext.menu.chat"     = "Chat — short, casual, emoji-friendly";
+"keyboard.appContext.menu.chat"     = "Chat — short, casual, natural tone";
 "keyboard.appContext.menu.document" = "Document — long-form, structured";
 "keyboard.appContext.menu.unknown"  = "General — neutral tone";