feat: shared PTY terminal (M12 Tier 3) + readable form controls

- feat(share): host-consented interactive terminal over the relay. The host shares
  a real PTY shell (core/pty_session.py); the guest renders it with pyte and sends
  keystrokes (gui/terminal_widget.py) — vim/top/tab-completion/Ctrl-C work. Runs as
  the host's user (never root). The host reads along live and can type too, e.g. a
  sudo password, which stays local and is never sent to the guest. Off by default.
  Guest also pulls inventory on join (req_full).
- fix(gui): style all form controls (QLineEdit/QPlainTextEdit/spin boxes/combo/
  terminals) dark-on-light-text — Fusion defaulted them to unreadable light-on-light.
- replaces the command/response shell with the full PTY; adds pyte to the gui extra.

Verified end-to-end against the deployed relay (guest keystroke ran on host PTY).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rigdoctor"
-version = "0.6.0"
+version = "0.7.0"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"
@@ -13,7 +13,7 @@ requires-python = ">=3.11"
 dependencies = []
 
 [project.optional-dependencies]
-gui = ["PySide6"]
+gui = ["PySide6", "pyte"]
 
 [project.scripts]
 rigdoctor = "rigdoctor.cli:main"