Python: feat(python): cross-channel hosting improvements (endpoint paths, Activity push, Telegram/Teams fixes) (#6307)

* Update hosting channel endpoint paths

Treat channel paths as concrete endpoint paths so built-in channels can be mounted at their defaults or at the app root without sample-specific subclasses. Update docs, tests, and the Foundry Telegram Invocations sample accordingly.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add push support to ActivityProtocolChannel

Implement the ChannelPush protocol so the Activity Protocol channel can
receive cross-channel fan-out (ResponseTarget.all_linked) and echo_input
replay as a non-originating destination:

- Add push() that reconstructs a proactive Bot Framework activity (bot/user
  swap) from the stored conversation reference and POSTs it to
  /v3/conversations/{id}/activities.
- Record a ChannelIdentity (service_url, conversation, bot, user, channel_id,
  locale) on ChannelRequest.identity so the host registers the channel under
  its isolation key for fan-out resolution.
- Route the streaming path through deliver_response so Activity-originated
  turns broadcast like Telegram/Discord.
- Add tests for push delivery, service_url validation, ChannelPush instance
  check, and inbound identity recording.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Don't delete Telegram webhook on shutdown by default

The TelegramChannel deleted its webhook on shutdown in webhook mode. During
a rolling redeploy the new revision registers the webhook on startup, then
the old revision's shutdown deletes it, silently breaking inbound delivery
until the next boot. setWebhook is overwriting/idempotent, so startup
re-asserts the webhook every boot and no teardown is needed.

Add a delete_webhook_on_shutdown flag (default False) so teardown is opt-in
for ephemeral deployments, and leave the webhook in place otherwise.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix Activity channel streaming on non-Teams channels (405 on updateActivity)

The Activity Protocol channel streamed replies the Teams way: POST a
placeholder, then PUT-edit it as tokens arrive. Only Teams supports the
updateActivity REST op; Web Chat, Direct Line and the Emulator return
405 Method Not Allowed on the PUT, so the user saw only the placeholder.

Gate the placeholder+edit flow on edit-capable channels (msteams). Other
channels now buffer the stream and POST a single final message, mirroring
the non-streaming path's fan-out and response-hook semantics. Also add a
defensive 405 fallback inside the Teams edit loop so an unexpected 405
can never strand the user on the placeholder.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(hosting-activity-protocol): don't parse Teams inline attachment content as a URI

Teams message activities include a text/html attachment whose inline
`content` is raw HTML (not a URL). _parse_activity fell back to
`attachment["content"]` and passed it to Content.from_uri, raising
ContentError ("URI must contain a scheme") and failing the whole turn,
so Teams users got no response.

Only treat `contentUrl` as a URI, require an absolute scheme, and skip
unparseable attachments defensively instead of failing the message.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat(hosting-activity-protocol): native slash-command dispatch for Teams/Activity

Add a commands= parameter to ActivityProtocolChannel that intercepts a
leading /command (after stripping the bot's own @mention) and dispatches
to ChannelCommand handlers, mirroring the Telegram channel. Unknown
commands fall through to the agent. The channel run_hook is applied to
command requests so handlers observe the same resolved isolation key as
ordinary messages, and handler errors are swallowed (200, no Bot Service
retry of non-idempotent commands).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat(hosting): silent attributed Telegram echoes + Teams markdown rendering

- hosting-telegram: send cross-channel input echoes with disable_notification
  (silent) and detect echo payloads so they aren't re-broadcast.
- hosting-activity-protocol: render outbound + push activities as textFormat
  'markdown' so Teams shows formatted replies (enables per-channel variants).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(hosting-activity-protocol): address PR #6307 review feedback

Consult the host delivery pipeline even for empty streamed replies so
ResponseTarget.none is honoured and non-originating fan-out is consulted
instead of always emitting an originating "(no response)" message. Applies
to both the progressive-edit (Teams) and buffered (Web Chat/Direct Line)
streaming paths.

Re-validate service_url against the allow-list in push(): the identity is
read from a persisted store and push runs out-of-band, so the captured
service_url must be re-checked before a bearer token is sent.

Adds tests for empty-stream host consultation/suppression on both streaming
paths and for push rejecting a disallowed service_url.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/hosting/tests/test_host.py

@@ -96,7 +96,7 @@ class _RecordingChannel:
         self.pushes: list[tuple[ChannelIdentity, HostedRunResult[Any]]] = []
         self._push_raises: Exception | None = None
         self._supports_push = supports_push
-        # Provide a single trivial route so contribute() exercises the mount path.
+        # Provide a single trivial route so contribute() exercises the endpoint path.
         self._routes: Sequence[BaseRoute] = (Route("/ping", _ping),)
 
     def contribute(self, context: ChannelContext) -> ChannelContribution:
@@ -239,6 +239,18 @@ class TestHostWiring:
             assert r.status_code == 200
             assert r.json() == {"ok": True}
 
+    def test_app_mounts_root_route_at_exact_channel_path(self) -> None:
+        agent = _FakeAgent()
+        ch = _RecordingChannel(path="/fake")
+        ch._routes = (Route("/", _ping),)
+        host = AgentFrameworkHost(target=agent, channels=[ch])
+
+        with TestClient(host.app, follow_redirects=False) as client:
+            r = client.get("/fake")
+            assert r.status_code == 200
+            assert r.json() == {"ok": True}
+            assert client.get("/fake/").status_code == 200
+
     def test_app_mounts_at_root_when_path_is_empty(self) -> None:
         agent = _FakeAgent()
         ch = _RecordingChannel(path="")