Retire the collector-facing emission pipeline

[zzylol]

Final step of #703 item 18, after #713, #715 and #718. Replaces #719, which was rebuilt on the current tree rather than replayed through #714's renames.

−23,503 / +801.

Why this lands as one commit

With the legacy planning endpoints gone (#718), the only remaining entry into the collector config chain was GET /api/v1/collector-config/agent, the HTTP config provider for collector bootstrap. Removing it retires the whole chain, because every part exists to serve that entry:

workloads.yaml startup pre-population
  → Analyzer / DeploymentPlanCompiler
  → PlanStore / WorkloadStore
  → Replanner (expiry + SLA-violation + backend-repost tickers)
  → Scraper (SLA violation detection)
  → OpAMP on-connect / on-disconnect hooks
  → colored_dag stage allocation + three-stage split
  → per-runtime YAML/TOML emitters

Splitting it would leave intermediate states that do not compile.

Deleted

emit/stage_config.rs (7,410), physical/colored_dag/ (2,572), replan.rs (1,350), emit/backend_push.rs (1,043), physical/workload_planner.rs (980), pipeline.rs (843), emit/{agent,otap,telegraf}.rs (1,857), registered_workload.rs (569), store/, monitor/, physical/{plan_cache,stage_split,topology}.rs, deployment_cost/{delta,sketch_capability}.rs plus its scoring layer, and the tests covering them.

registered_workload.rs is new since the first attempt — #714 introduced it as the unified planner workload, but it only ever served the legacy chain, so it retires with it.

Also gone: the USE_TYPED_STAGE_SPLIT kill switch (#703 item 12 — its "off" branch was the legacy emitter), RealizationProvider::stages (item 10, no callers), physical/topology.rs (item 11, a pure re-export).

Extracted, not deleted

• physical::backend_stage (87 lines) keeps BackendStageConfig, BackendAggregation, BackendReadout, AggregationInput. PhysicalPlanCompiler builds these; backend_plan::from_stage_config consumes them. Their collector-side neighbours (EdgeStageConfig, GatewayStageConfig, ExportTarget, StageId) do not come along.
• emit::backend_wire (390 lines) keeps the storage-routing classifier and build_backend_aggregation_json. That builder stays the single source of the aggregation wire shape, so BackendPlan materializations and the JSON format keep one PolicyFingerprint identity space — the invariant from_stage_config's module doc calls load-bearing.

deployment_cost keeps only what still has consumers: online (/api/v1/cost-model), tco (/api/v1/tco), wire (post-ASAP cost model). SketchCosts and the benchmark table move into online, its only remaining caller.

Behaviour changes

• /metrics no longer exposes asap_active_plan_id. The gauge read PlanStore, which was legacy plan history. Every asap_runtime_* gauge is unchanged.
• GET /api/v1/collector-config/agent is gone. The OpAMP CollectorPlan channel stays — ASAPCollector's asapedgeprocessor already implements ReceiveCollectorPlan — but a deployment pointing a collector at --config=http://control_plane:8080/api/v1/collector-config/agent has to move to that channel.

The e2e test

data_plane/tests/e2e_controller_plans_and_backend_serves.rs built its config through the deleted chain. Its scaffolding is ported here — plan_materializations runs BackendLocalPlanningInput::into_physical_compilation_request → PhysicalPlanCompiler::compile_promql, and physical_fixture::artifact_from_materializations takes planner output directly, so the legacy StreamingConfig document is no longer an intermediate step.

The 12 tests are #[ignore]d, tracked by #723. Making them pass is a different problem from making them compile: they build their OTLP payloads from summary families the legacy path was told to use via sketch_type_override, which ASAPPlanner has no equivalent for. Measured, not assumed:

test	old override	planner's choice
..._roundtrip_kll	KLL	DDSketch
..._roundtrip_count_sketch	CountSketch	CountMinSketchWithHeap
..._roundtrip_count_min_sketch	CountMinSketch	CountMinSketchWithHeap

#723 carries the five remaining failure classes and their root causes. This is the work #703 item 2 already scoped separately.

Resulting surface

Production routes are the ASAPPlanner path only:

/api/v1/physical-plan/cost-manifests
/api/v1/metricsql/physical-plan/cost-manifests
/api/v1/physical-plan/compile-and-publish
/api/v1/metricsql/physical-plan/compile-and-publish
/api/v1/clickhouse-plan/compile-and-publish
/api/v1/cost-model
/api/v1/tco
/metrics

AppState is down to opamp, online_store, runtime_samples, active_summary_catalog, backend_client. OpampServer is constructed bare and retains only publish_collector_plans, which the physical path uses.

Testing

• cargo +1.98.0 fmt -- --check — clean.
• cargo +1.98.0 clippy --workspace --all-targets -- -D warnings — clean.
• cargo +1.98.0 test --workspace -- --test-threads=1 — exit 0, zero failures.

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