[ishandhanani]

Summary

Stacked on #93. That PR gives classifiers a per-request snapshot of worker inputs, taken before classify. This PR adds the live view it deferred: RequestClassifierContext::worker_loads() reads the router's current load on every registered worker rank each time it is called. A classifier that holds requests, such as ThunderAgent, can call it when it decides to release one.

• worker_loads() returns Option<Vec<(WorkerWithDpRank, WorkerLoadInput)>>. It is None when the host attaches no load reader, for example in contexts built only with RequestClassifierContext::new.
• The KV router attaches the reader in KvRouter::request_classifier_context() through LocalScheduler::worker_load_reader(). The reader projects load with project_worker_loads(None, now), the same projection the scheduler actor uses.
• WorkerLoadInput::from_projection is now the single conversion that worker selection, the feat(router): expose worker inputs to request classifiers #93 snapshot, and this live view all use.

Meaning: no request is attached, so decode_cost_blocks is the current decode footprint. In read_worker_inputs it also includes that request's uncached prompt blocks. Values come from the router's own bookings, not engine KV occupancy. Each call is one pass over registered ranks under the load table's read lock, with no prefix-trie walk.

ThunderAgent is unchanged. Moving its release loop to host load is a separate change. It would need to replace its normal_usage estimate, not add to it, because host load already counts the requests it admitted.

Validation

• cargo test -p dynamo-kv-router --lib: 1082 passed. The new worker_load_reader_reads_current_load creates one reader, books a request after that, and checks that the same reader reports the booking (active_requests 0 to 1).
• cargo test -p dynamo-llm --lib -- kv_router::tests::classifier_context_tracks_capacity_and_registered_ranks: passed, with a new assertion that the router context exposes worker_loads().
• cargo test -p dynamo-custom-policy-builtin: all passed.
• cargo clippy -p dynamo-kv-router -p dynamo-custom-policy-builtin --all-targets --features dynamo-kv-router/bench -- -D warnings and cargo clippy -p dynamo-llm --lib -- -D warnings: clean.
• pre-commit run on the changed files: passed.