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/plugin.yaml

@@ -0,0 +1,9 @@
+name: teams_pipeline
+version: 0.1.0
+description: "Microsoft Teams meeting pipeline plugin with durable runtime state and operator CLI flows for Graph-backed transcript-first meeting summaries."
+author: NousResearch
+kind: standalone
+platforms:
+  - linux
+  - macos
+  - windows