fix: planner binds all 6 contract metrics into routing table (HLL/CountSketch/CountMin)

[zzylol]

Summary

The 5-sketch routing-connector wire YAML emitted by the bootstrap GET
(/api/v1/collector-config/agent) was missing 3 of the 6 MVP §46 contract
metrics. Symptom from the live demo:

http_requests_total_latency_ms → ddsketch_path        ✅
request_size_bytes              → kll_path             ✅
http_freshness_probe_warm       → raw_passthrough      ✅ (demo plumbing)
http_freshness_probe_archive    → raw_passthrough      ✅ (demo plumbing)
unique_users_per_min            → should hit hll_path           ❌
top_endpoint_qps                → should hit countsketch_path   ❌
endpoint_request_freq           → should hit countminsketch_path ❌

The workload registry loaded all 8 entries (count=8), but
collect_metric_to_family walked them and only emitted 2 sketched routes.

Root cause — two missing stitches

1. WorkloadEntry silently ignored sketch_family_override. The struct in
   controller/src/config/workloads.rs had no field for it; serde defaults
   to ignoring unknown fields, so the operator's sketch_family_override: HLL / CountSketch / CountMinSketch round-tripped to None. The
   pre-pop loop in main() then passed QuerySpec.sketch_type = None to
   the analyzer.

2. bind_workload_typed early-returned on w.exact_required = true at
   controller/src/planner/rules.rs:81. The PromQL parser sets that flag
   when the inner walk synthesises an AggFunc::Sum over a bare
   VectorSelector — which happens for count(metric),
   topk(K, metric), and rate(metric[5m]) (the query_strings on
   workload entries 6, 7, 8). The metric-name match in
   classify_demo_metric and the sketch_type_override field never got
   consulted because the early return happened first.

   Carved out an exception: when the metric is a contract row
   (classify_demo_metric returns Some) or carries an explicit override,
   those signals win over exact_required because both are explicit
   "sketch this metric" instructions.

Files

• controller/src/config/workloads.rs — add sketch_family_override
  (case-insensitive SketchType deserialiser) and target_path fields
  to WorkloadEntry; new WorkloadRegistry::from_entries for testing.
• controller/src/main.rs — thread entry.sketch_family_override into
  QuerySpec.sketch_type in the registry pre-pop loop (lines ~234).
• controller/src/planner/rules.rs:81-99 — guard the exact_required
  early-return with the contract-row / operator-override carve-out.
• controller/src/config/mod.rs + controller/src/main.rs — new tests.

Curl evidence (after fix)

$ CONTROLLER_WORKLOADS=deploy/configs/mvp-workload.yaml \
  USE_TYPED_STAGE_SPLIT=1 ./controller &
$ curl -s http://localhost:8080/api/v1/collector-config/agent \
       -H 'X-Agent-Runtime: AsapOtel' | grep metric.name
    - statement: route() where metric.name == "endpoint_request_freq"
    - statement: route() where metric.name == "http_requests_total_latency_ms"
    - statement: route() where metric.name == "request_size_bytes"
    - statement: route() where metric.name == "top_endpoint_qps"
    - statement: route() where metric.name == "unique_users_per_min"
    - statement: route() where metric.name == "http_freshness_probe_warm"
    - statement: route() where metric.name == "http_freshness_probe_archive"

5 sketched metric routes (DDSketch / KLL / HLL / CountSketch /
CountMinSketch) + 2 freshness probes — full 5-sketch coverage.

Test plan

• cargo test --release --bin controller — 608 passed (was 603 on
  origin/main; +5 new tests, +0 regressions; same 10 pre-existing failures).
• New regression bootstrap_routing_table_covers_all_five_sketches_for_live_mvp_yaml
  pins the contract: registry-walk path produces a 5-entry routing
  table for the live deploy/configs/mvp-workload.yaml shape.
• Live curl against a controller pointed at the deployed YAML
  confirms all 5 sketched metrics + both freshness probes route correctly.
• live_mvp_workload_yaml_loads_with_overrides smoke-tests the
  actual deploy file deserialises with all four overrides intact.

Closes #46.

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