fix(tui): preserve launch context in resume commands

[Wsp030914]

Summary

• preserve explicit --config and --workspace selectors in TUI resume commands
• apply the same launch context to both normal exit and /detach
• quote selector paths for POSIX shells and PowerShell
• keep implicit defaults implicit
• add regression tests and update documentation

Reproduction

1. Start the native TUI with a valid non-default config and workspace:

   nanobot agent --config 'C:\tmp\nanobot alt\config.json' --workspace 'C:\tmp\nanobot alt\workspace'

2. Start or select a session.

3. Exit the TUI, or use /detach.

4. Observe the printed resume command.

Before this fix, the command contains only the session ID:

nanobot agent --session websocket:<chat-id>

5. Run that command from another directory or environment using the default
   nanobot configuration.

Actual behavior

The explicit config and workspace selectors are lost. The resume command may
connect to the default nanobot instance instead of reopening the session in its
original launch context.

Expected behavior

The printed command preserves the explicitly supplied selectors:

nanobot agent --config 'C:\tmp\nanobot alt\config.json' --workspace 'C:\tmp\nanobot alt\workspace' --session websocket:<chat-id>

When no selectors were explicitly supplied, the existing short command should
remain unchanged.

Implementation

The Python TUI launcher forwards only explicitly supplied config and workspace
selectors through TUI-specific environment variables.

The TUI uses those values only when formatting resume commands. The canonical
config path used internally by the gateway remains unchanged.

Testing

• uv run --no-sync pytest tests/cli/test_tui_launcher.py -q
• uv run --no-sync ruff check nanobot/cli/agent.py nanobot/cli/tui_launcher.py tests/cli/test_tui_launcher.py
• uv run --no-sync basedpyright nanobot/cli/agent.py nanobot/cli/tui_launcher.py
• cd tui && bun run check
• cd tui && bun run test
• cd tui && bun run build
• git diff --check
• manually verified the resume command on PowerShell

Follow-up to #5452 and #5461.