Remove ActivitySender send abstraction

[heyitsaamir]

Removes the separate ActivitySender class while preserving its send behavior.

Why:
ActivitySender had become a second send path. With AgenticIdentity support, the API client owns service URL resolution and request auth, so activity sends should route through the same API client path.

Interesting bits:

• send_or_update_activity keeps the old ActivitySender contract without keeping the class.
• Preserves create vs update behavior when activity.id is set.
• Preserves targeted create/update routing through create_targeted / update_targeted.
• Preserves activity.from_ = ref.bot and activity.conversation = ref.conversation stamping.
• Preserves targeted-in-personal-chat validation.
• ActivityContext still creates HttpStream directly from its scoped API client.

Reviewer tips:
Start with activity_send.py, then check ActivityContext.send, App.send, and FunctionContext.send.

Testing:

• Focused app send/reply/function/quoted-reply tests covering the old ActivitySender behavior.
• Ruff on touched app send files and tests.

[heyitsaamir]

This change is part of the following stack:

• [FEATURE BRANCH]-DNP Start Agent 365 support branch #464
  • Remove ActivitySender send abstraction #479 ◀
    • Add app-level agentic send helpers #480

_{Change managed by git-spice.}

[corinagum]

Removing ActivitySender is the right call, but it's introducing behavior regression between what people calling through it would experience vs. api.conversation...create() directly

[Copilot]

Pull request overview

This PR removes the ActivitySender abstraction from the apps package and reroutes App.send, ActivityContext.send, and FunctionContext.send through the API client’s conversations.activities(...).create(...) pathway, updating unit tests accordingly. It also keeps streaming support by having ActivityContext construct HttpStream directly from its scoped ApiClient.

Changes:

• Removed ActivitySender and updated app/context send flows to call the Conversations Activities API client directly.
• Refactored ActivityContext streaming initialization to be lazy via HttpStream(self.api, self.conversation_ref).
• Updated tests to mock conversations.activities(...).create(...) rather than activity_sender.send(...); deleted ActivitySender unit tests.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/apps/src/microsoft_teams/apps/routing/activity_context.py	Removes ActivitySender dependency, adds lazy stream, and routes send() through API client create.
packages/apps/src/microsoft_teams/apps/contexts/function_context.py	Routes send() through API client create and sets basic outbound activity fields.
packages/apps/src/microsoft_teams/apps/app.py	Removes ActivitySender initialization and routes proactive send() through API client create.
packages/apps/src/microsoft_teams/apps/app_process.py	Removes ActivitySender injection and builds ActivityContext without it.
packages/apps/src/microsoft_teams/apps/activity_sender.py	Deleted ActivitySender implementation.
packages/apps/tests/test_activity_context.py	Updates mocks/expectations to observe API client create calls instead of sender calls.
packages/apps/tests/test_quoted_reply.py	Updates reply/quote tests to read arguments passed to API client create.
packages/apps/tests/test_function_context.py	Updates tests to validate API client create call path and return type.
packages/apps/tests/test_app.py	Updates send/reply tests to mock the API create path.
packages/apps/tests/test_app_process.py	Updates processor tests to patch ApiClient/HttpStream instead of ActivitySender.
packages/apps/tests/test_app_oauth.py	Removes activity_sender argument from context construction.
packages/apps/tests/test_optional_graph_dependencies.py	Removes activity_sender argument from context construction.
packages/apps/tests/test_activity_sender.py	Deleted tests for removed ActivitySender.

[heyitsaamir]

@corinagum the logic's updated again to move us to a utility that handles the complexities around sending. It's hared between ctx.send and app.send

[corinagum]

LGTM!