Closes followup #14 (runtime YDB-version drift) and stages 4b.1+4b.2
of the m-engine plan. Coordinated with m-test-engine commit 1e7a4cc
(Phase 4a: docker/mte introspection script).

* engine_driver.py
  - `DockerDriver.mte_status()` — shells out to `docker exec <container>
    mte status --json`; returns parsed dict or None (graceful on
    non-zero rc, garbage output, container down).
  - `EngineStatus.mte: dict | None` (default None). `to_dict()`
    serialises it.
  - `DockerDriver.status(*, verbose=False)` — verbose=True populates
    `mte` and adds `runtime_ydb_version_drift` to mismatches when
    `mte["release"]` != `manifest.ydb_version`. De-duped against the
    static-label `ydb_version_drift` from Phase 3b.
  - Protocol grew `mte_status()` and the `verbose` kwarg on `status()`.

* engine_cli.py
  - `m engine status --verbose / -v` flag wired; text output gains an
    "inside container (mte):" block with release/uptime/globals/
    routines/mounted_repos. `--json` output gets the mte block via
    EngineStatus.to_dict().
  - `m engine watch` (new) — long-running poll of `mte_status()`;
    emits one JSON-lines record per poll with `ts` wall-clock
    timestamp. `--interval` (default 5s, min 0.1) controls cadence;
    `--count N` caps the loop (`0` = until SIGINT). KeyboardInterrupt
    → clean exit rc 0.
  - `m engine capabilities` payload advertises `watch` as
    read_only:true.

* tests/test_engine_driver.py — 8 new tests for mte_status() (parse /
  None on bad rc / None on garbage), status verbose folding, drift
  detection, non-verbose skip, container-down skip.

* tests/test_engine_cli.py — 5 new tests for --verbose pass-through,
  text/JSON rendering, watch JSON-lines + error-line behaviour.

* tests/test_doctor.py — single drive-by fix to
  `test_doctor_cli_exits_one_when_any_fail`: monkeypatch
  `docker_available` → False so the existing demote-when-engine-OK
  path (a separate prior addition implementing followup #6) doesn't
  override the test's expected `ydb_dist=FAIL` on hosts where docker
  is healthy. Preserves the test's original intent without depending
  on the local environment.

Full suite 1471 passing / 1 skipped (was 1453); ruff + mypy clean.
Live `m engine status --verbose` on this host correctly detected
`runtime_ydb_version_drift` because the running image is V7.1-002
(yottadb-base:latest-master tip) while the manifest declares
`ydb_version: "r2.02"`. `m engine watch --interval 0.2 --count 2`
emitted 2 valid JSON-lines records.

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