feat(teams-pipeline): add plugin runtime and operator cli

Third slice of the Microsoft Teams meeting pipeline stack, salvaged
onto current main. Adds the standalone teams_pipeline plugin that
consumes Graph change notifications from the webhook listener,
resolves meeting artifacts (transcript first, recording + STT fallback
later), persists job state in a durable store, and exposes an operator
CLI for inspection, replay, subscription management, and validation.

Design choices follow maintainer review feedback on PR #19815:

- Standalone plugin rather than bolted-on core surface
  (plugins/teams_pipeline/, kind: standalone in plugin.yaml).
- Zero new model tools. The agent drives the pipeline by invoking
  the operator CLI via the terminal tool, guided by the skill that
  ships with a follow-up PR.
- Reuses the existing msgraph_webhook gateway platform for Graph
  ingress. Pipeline runtime is wired in via bind_gateway_runtime and
  gated on plugins.enabled so gateways that don't run the plugin
  boot cleanly.

Additions:

- plugins/teams_pipeline/: runtime (gateway wiring + config builder),
  pipeline core, durable SQLite store, subscription maintenance
  helpers, Graph artifact resolution, operator CLI (list, show,
  run/replay, fetch dry-run, subscriptions list, subscribe,
  renew-subscription, delete-subscription, maintain-subscriptions,
  token-health, validate).
- hermes_cli/main.py: second-pass plugin CLI discovery so any
  standalone plugin registered via ctx.register_cli_command()
  outside the memory-plugin convention path gets its subcommand
  wired into argparse without touching core.
- gateway/run.py: _teams_pipeline_plugin_enabled() config gate,
  _wire_teams_pipeline_runtime() binding after adapter setup, and
  the two runner attributes used by the runtime.

Credit to @dlkakbs for the entire plugin implementation.

plugins/teams_pipeline/__init__.py

@@ -0,0 +1,23 @@
+"""Teams meeting pipeline plugin.
+
+Registers only operator-facing CLI surfaces. The agent should invoke these via
+the terminal tool; no model tools are added by this plugin.
+"""
+
+from __future__ import annotations
+
+from plugins.teams_pipeline.cli import register_cli, teams_pipeline_command
+
+
+def register(ctx) -> None:
+    ctx.register_cli_command(
+        name="teams-pipeline",
+        help="Inspect and operate the Microsoft Teams meeting pipeline",
+        setup_fn=register_cli,
+        handler_fn=teams_pipeline_command,
+        description=(
+            "Operator CLI for the Microsoft Teams meeting pipeline. "
+            "Lists jobs, inspects stored runs, replays jobs, validates Graph "
+            "setup, and maintains Graph subscriptions."
+        ),
+    )