feat: session status at a glance, file & image drop, live Ops Alerts (0.4.0)

- devdesk-state-hook (Claude UserPromptSubmit/PostToolUse/Notification/Stop/
  SessionStart/SessionEnd) records whether each session is working, waiting on
  you or idle; --list carries it. The sidebar shows it, the header shows the
  current session's state, and a pulsing "needs you" chip jumps to sessions
  waiting for input. Session refresh no longer depends on the sidebar being open.
- `devdesk attach --upload SESSION FILE BYTES` receives a file as base64
  terminal input (raw mode, exact length, size-checked, sanitised name) into
  /var/lib/devdesk/uploads/<session>/. The UI uploads dropped or pasted files and
  pastes the path into Claude, which attaches images itself.
- `devdesk alerts` / `--alerts`: firing and pending Grafana alert rules with
  severity, instances, summary and a link. The panel's "Ask Claude" types an
  investigation prompt into the current session.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Makefile

@@ -40,7 +40,7 @@ install: all
 	install -m 0644 libexec/devdesk-lib.sh $(DESTDIR)$(LIBDIR)/devdesk-lib.sh
 	install -m 0755 libexec/devdesk-picker libexec/devdesk-claude-run libexec/devdesk-session-hook \
 		libexec/devdesk-tmux-ready libexec/devdesk-serve libexec/devdesk-statusline \
-		libexec/devdesk-deploy $(DESTDIR)$(LIBDIR)/
+		libexec/devdesk-deploy libexec/devdesk-state-hook $(DESTDIR)$(LIBDIR)/
 	install -m 0755 build/ttyd $(DESTDIR)$(LIBDIR)/bin/ttyd
 	install -m 0644 dist/index.html share/tmux.conf share/claude-settings.json $(DESTDIR)$(SHAREDIR)/
 	install -m 0644 etc/env $(DESTDIR)$(SYSCONFDIR)/devdesk/env