feat: agentic chat tab — tools, MCP bridge, terax-style step UI, sub-agent spawning

- Live streaming with full agentic loop (stepCountIs 24) via AI SDK streamText
- Six chat tools: read_file, list_files, run_git_log, run_git_status,
  propose_agent_task (with model field), and dynamic atlas_* tools via MCP
- Atlas MCP bridge in Rust: spawns node server-entry.js, full JSON-RPC
  handshake including roots/list reply to prevent deadlock
- Terax-style agentic step cards: 6px status dot (amber pulse to hollow),
  lucide icon + label + mono args preview, CSS grid height animation (240ms),
  shimmer thinking indicator, fade-in slide-from-bottom on mount
- Proposal card persists across tab close/reopen with launched state
  shown as white button with black text; dismissed state also persisted
- Full chat history persistence: saves complete MessagePart[] array
  including tool calls and proposals, not just text content
- Sub-agent spawning: propose_agent_task carries agent + model + task prompt;
  Launch opens agent tab in background, user stays on chat tab
- Model selection: --model flag prepended to agent CLI args for claude,
  gemini, and codex so specific model variant is used
- Background agent fix: openSession sends resize_pty immediately after
  spawn so agent CLI gets real terminal dimensions and starts without
  requiring tab focus
- setWorkState working set immediately on launch so tab badge shows
- / command palette and @ file picker with dedicated search bar and Geist font
- @ file mention chips read file contents and prepend as context
- System prompt passed as system param fixing AI_InvalidPromptError
- New Rust commands: git_recent_commits, git_remote_url, git_ls_files,
  read_file, list_directory, atlas MCP bridge commands
- README: removed personal email addresses

Co-authored-by: Tempest <tempestai.dev@gmail.com>

Author: gsvprharsha

README.md

@@ -96,3 +96,4 @@ npm run build      # production build -> dist-installers/
 [Instagram](https://instagram.com/usetempest)
 
 [LinkedIn](https://linkedin.com/company/usetempest)
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