feat: unify extract_promql_call with controller — single PromQL → Capability owner

[zzylol]

Summary

Today the warm-tier reducer's extract_promql_call did a naive AST walk to extract (function_name, args) from a PromQL query. This duplicated knowledge the controller already encodes (PromQL → Intent → Capability via query_parser, intent_algebra, sketch_algebra, algebra::lower) and silently routed the MVP demo's compound queries (e.g. sum by (zone) (rate(http_requests_total[5m])), histogram_quantile(0.99, sum(rate(bucket[5m])) by (le))) through the archive engine because the outermost-call heuristic returned None on nested shapes.

The controller is now the single owner of "is this PromQL warm-tier-answerable" knowledge.

Design

                  ┌─ Step 1 (controller, ingest plane) ────────┐
PromQL +          │  intent_algebra::AggIntent                  │  →  Agent configs
streaming-config →│  algebra::lower → physical plan             │
                  │  sketch_algebra::capability_for             │
                  │  planner::stage_split                       │
                  └─────────────────────────────────────────────┘

                  ┌─ Step 2 (backend, query plane) ────────────┐
Live PromQL    →  │  controller::warm_tier_analysis ::          │ → SketchReducer
                  │     analyze_promql_for_warm_tier            │   OR archive
                  │  (was: extract_promql_call in asap-query-   │
                  │   engine — deleted)                         │
                  └─────────────────────────────────────────────┘

Both steps now share the controller's PromQL → Capability mapping.

API surface

pub fn analyze_promql_for_warm_tier(promql: &str) -> WarmTierAnalysis;

pub struct WarmTierCandidate {
    pub metric_name: String,
    pub group_by_keys: BTreeSet<String>,
    pub required_capability: Capability,
    pub function: String,
    pub function_args: Vec<f64>,
    pub range_seconds: u64,
}

pub enum UnsupportedReason {
    UnsupportedFunction(String),
    UnsupportedComposition(String),
    NoCallNodeFound,
    UnparseablePromql(String),
}

PromQL shape coverage

Shape	Capability / behavior
quantile_over_time(q, m[r])	QuantileApprox(Any)
histogram_quantile(q, m)	QuantileApprox(Any)
count_distinct_over_time(m[r])	CardinalityApprox
cardinality_estimate(m)	CardinalityApprox
topk(k, m)	FrequencyTopk(CmsWithHeap)
topk_over_time(k, m[r])	FrequencyTopk(CmsWithHeap)
sum by(…) (rate(m[r]))	UnsupportedFunction("rate") → archive
histogram_quantile(q, sum(rate(…)) by(le))	same → archive
sum by(…) (m)	UnsupportedComposition (Sum-over-CountSketch is a follow-up)
increase / irate	UnsupportedFunction → archive
topk(k, rate(m[r]))	UnsupportedComposition → archive
bare m{filters}	NoCallNodeFound → archive

Boundary types

Controller exposes its own Capability + SketchKindHandle enums in warm_tier_analysis. Backend's sketch_index.rs gains From<…> adapters + Capability::is_satisfied_by(indexed) helper that handles the SketchKindHandle::Any wildcard (e.g. QuantileApprox(Any) is satisfied by both DDSketch and KLL indexed instances). Avoids a workspace-dep cycle.

Build + test

• cargo build --release -p query_engine_rust clean
• cargo build --release -p controller clean
• cargo test --release -p query_engine_rust --lib -- engines::warm_tier — 13/13 pass

Diff

asap-query-engine/src/engines/simple/engine.rs           |  98 +/-
asap-query-engine/src/engines/warm_tier/mod.rs           |  20 +/-
asap-query-engine/src/engines/warm_tier/promql_extract.rs| 159 --- (deleted)
asap-query-engine/src/stores/sketch_db/sketch_index.rs   |  85 +
controller/src/lib.rs                                    |   5 +
controller/src/warm_tier_analysis.rs                     | 775 + (new)
6 files changed, 1166 insertions(+), 309 deletions(-)

Follow-ups (out of scope here)

• Per-candidate hybrid stitch (PR feat: warm-tier follow-ups — FrequencyTopk + Delta encoding + Hybrid stitch #126 stitches at engine level; per-candidate is a future PR).
• Sum-over-CountSketch reducer for the sum by (zone) (metric) shape.
• Wire the analyzer's range_seconds into SketchReducer.evaluate(t0, t1) bounds — today the dispatch uses [now - 5min, now].

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