Chat Mentions

• When changing app mention syntax or parsing, keep all chat mention paths aligned: shared parsing in src/shared/parse_mention_apps.ts, referenced-app extraction in src/ipc/utils/mention_apps.ts, and Lexical external value sync in src/components/chat/LexicalChatInput.tsx. Saved values like @app:foo.app.com must render back as one mention node, not a shortened mention plus plain text; terminal sentence dots such as @app:foo.app.com. should remain plain text outside the mention node.
• LexicalChatInput must never clear itself on submit — clearing is caller-owned. On a successful submit the caller sets the input value to "" (home's handleSubmit, ChatInput's clearComposerAfterSubmit), which triggers the editor's external-clear effect. A rejected or queued submit (no provider configured → pending first prompt; failed queue mid-stream) must leave the value intact: if the home input is emptied while pendingFirstPromptAtom stays true, the armed auto-resume effect in home.tsx submits the user's next keystroke instead of the original prompt.