refactor(agent): let runner own context compaction (#5568)

* refactor(agent): consolidate accepted history under pressure

* fix(agent): align provider and session compaction

* refactor(agent): simplify runner context compaction

* refactor(agent): remove background token consolidation

* fix(agent): keep injected transcript messages distinct

* refactor(agent): unify native compaction summaries

* fix(agent): preserve native compaction boundary

* fix(agent): unify context compaction paths

* fix(agent): preserve exact compaction request boundaries

tests/agent/test_loop_runner_integration.py

@@ -112,7 +112,6 @@ async def test_goal_command_can_implement_plan_from_prior_discussion(tmp_path):
         LLMResponse(content="done", tool_calls=[], usage=None),
     ])
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=None)
     session = loop.sessions.get_or_create("cli:direct")
     session.add_message("user", "Let's agree on the migration implementation.")
     session.add_message("assistant", "Use the staged migration plan and run integration tests.")
@@ -166,7 +165,6 @@ async def test_runtime_context_is_persisted_as_next_turn_prompt_prefix(tmp_path)
         LLMResponse(content="second answer", usage=None),
     ])
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=None)
     session = loop.sessions.get_or_create("cli:direct")
     provider_calls: list[str | None] = []
 
@@ -220,7 +218,6 @@ async def test_webui_quote_reaches_model_without_leaking_into_public_history(tmp
     provider.generation = GenerationSettings()
     provider.chat_with_retry = AsyncMock(return_value=LLMResponse(content="answer", usage=None))
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=None)
     session = loop.sessions.get_or_create("websocket:chat")
     quote = webui_quote_runtime_context({
         WEBUI_QUOTE_METADATA: "the selected answer excerpt",
@@ -265,7 +262,6 @@ async def test_runtime_context_provider_runs_once_across_tool_iterations(tmp_pat
         LLMResponse(content="done", usage=None),
     ])
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=None)
     provider_calls = 0
 
     async def provide_context(_request):
@@ -310,7 +306,6 @@ async def test_non_goal_direct_turn_cannot_reuse_prior_goal_command(tmp_path):
         LLMResponse(content="handled as a one-time task", tool_calls=[], usage=None),
     ])
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=None)
     session = loop.sessions.get_or_create("api:default")
     session.add_message("user", "/goal old completed request")
     session.add_message("assistant", "The old request is complete.")
@@ -589,7 +584,6 @@ async def test_next_turn_after_llm_error_keeps_turn_boundary(tmp_path):
 
     loop = AgentLoop(bus=MessageBus(), provider=provider, workspace=tmp_path, model="test-model")
     loop.tools.get_definitions = MagicMock(return_value=[])
-    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=False)  # type: ignore[method-assign]
 
     first = await loop._process_message(
         InboundMessage(channel="cli", sender_id="user", chat_id="test", content="first question")