Initial commit: hqt — HQ Terminal TUI

TUI for orchestrating AI coding harness sessions (Claude Code, Codex,
Kiro, etc.) via tmux. Click CLI bootstraps a Textual TUI over
ProjectService/SessionService backed by SQLite, spawning harness
sessions as tmux windows through TmuxManager.

Includes recent fixes:
- Visible Tab focus highlight on dialog OK/Cancel buttons
- Auto-select first project on launch
- Auto-select first session + per-project session-selection memory
- tmux new-window targets an explicit free index, fixing
  "index N in use" failures (broken spawn/attach in attached sessions)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.hq/LESSONS.md

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+# Lessons
+
+## 2026-06-09: tmux windows vs sessions
+- **Symptom:** Enter/Shift+R on sessions did nothing; `tmux list-sessions` only showed main session
+- **Cause:** Harness sessions were separate tmux sessions. `switch-client` moves the entire client away. Sessions died silently with no error feedback.
+- **Fix:** Redesigned to use windows within a single `hqt-main` session. `select-window` stays in context. `remain-on-exit` + `respawn-pane` handles dead processes cleanly.
+- **Signal:** If "attach" ever silently fails again, check: does the tmux target actually exist? Is the error being swallowed?
+
+## General
+- tmux `remain-on-exit` must be set BEFORE the command can exit (race condition if set after `new-session`/`new-window`)
+- `respawn-pane -k` restarts a dead pane in-place without destroying the window — preferred over kill+recreate
+- Always check and propagate tmux command return codes; silent failures are the worst debugging experience