feat(watchdog): proc_blocking alert for orphaned long-lived test processes

Close the observability gap between agent_hung (only tracked jobs by jobs.pid)
and orphaned pytest subprocesses the orchestrator launches itself
(merge_gate.retest_branch / coverage_gate.measure_coverage). On a timeout-kill of
the agent (-9, ORCH-109) the grand-child pytest reparents onto tini and keeps
running for days, starving CPU and failing merge-gate re-test — with no alert.

Strictly inside the observer (watchdog/** + the watchdog compose service):
- watchdog/collectors/proc.py: stdlib-only /proc scan (under pid: host),
  read-only, never-raise -> []; pure parsers split from I/O (tested on a fake
  /proc tree). Never reads /proc/<pid>/environ.
- watchdog/signals.py: pure proc_signals builder, per-entity
  ("proc_blocking", pid), active iff age_s > proc_age_s; actionable RU detail.
- watchdog/core.py: opt-in tick block (gated on proc_enabled -> zero overhead /
  byte-for-byte when off) + RECOVERY synthesis for a vanished process through the
  existing decide()/AlertState (no new anti-spam logic).
- watchdog/config.py: WATCHDOG_PROC_{ENABLED(false),AGE_MIN(60),PATTERNS(pytest),
  COOLDOWN_S(1800)}; default threshold > max(merge_retest_timeout_s=600,
  coverage_run_timeout_s=900) so a legit in-flight run never crosses it.
- docker-compose.yml: pid: host on orchestrator-watchdog ONLY (read-only privilege).

Anti-false-positive and no overlap with agent_hung are by construction (cmdline
scope + age threshold), not fragile cross-namespace PID matching.

Canon synced: WATCHDOG_PROC_* in .env.watchdog.example <-> .env.example block;
documented in LITE_SETUP.md and docs/architecture/README.md (architect). src/**,
/metrics, schema_version, STAGE_TRANSITIONS, QG_CHECKS, check_*, machine-verdict
and the DB schema are untouched; deploy rebuilds only the sidecar, prod
orchestrator is not restarted (NFR-3).

Tests: tests/watchdog/test_proc_blocking_signal.py (TC-01..TC-06),
test_proc_collector.py (/proc parsing), test_tick_proc_blocking_integration.py
(TC-07), plus pid: host and proc-config assertions. Full pytest tests/ green (1930).

Refs: ORCH-111
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/deployment/LITE_SETUP.md

@@ -163,6 +163,18 @@ cp .env.watchdog.example .env.watchdog
 # заполнить два ключа: WATCHDOG_TG_BOT_TOKEN / WATCHDOG_TG_CHAT_ID (бота создадим в §8)
 ```
 
+**Опционально (ORCH-111): алерт на осиротевший тест-процесс.** Watchdog умеет
+поднимать сигнал `proc_blocking` на долго живущий процесс тест-класса (по умолчанию
+`pytest`), репарентированный на хост и грузящий CPU. По умолчанию **выключен**
+(`WATCHDOG_PROC_ENABLED=false`) — нулевая регрессия. Чтобы включить, в `.env.watchdog`:
+`WATCHDOG_PROC_ENABLED=true`, при необходимости подстройте `WATCHDOG_PROC_AGE_MIN`
+(минуты; **обязан** превышать `max(merge_retest_timeout_s, coverage_run_timeout_s)/60`,
+дефолт 60), `WATCHDOG_PROC_PATTERNS` (CSV cmdline-подстрок), `WATCHDOG_PROC_COOLDOWN_S`.
+Для видимости процессов хоста сервису `orchestrator-watchdog` в `docker-compose.yml`
+задан `pid: host` (привилегия только у наблюдателя, read-only). **Проверка:**
+`grep -E '^WATCHDOG_PROC_ENABLED=' .env.watchdog` — если `true`, после рестарта только
+sidecar (`docker compose up -d orchestrator-watchdog`) в его логах виден тик без ошибок.
+
 **Проверка (резолв всей конфигурации):**
 
 ```bash