feat(libsy): Pass models at runtime not construction time - #630

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Inline comments:
In `@benchmark/routing-profiles/tau2-telecom-custom-opus-qwen-aggressive.toml`:
- Around line 76-79: Update both classifier prompts to replace all legacy
WEAK/STRONG and weak/strong routing labels with the schema values efficient and
capable, using efficient for routine requests and capable for escalation; keep
the response_schema and direct route-output requirement consistent.

In `@crates/libsy/src/algorithms/fall_through.rs`:
- Line 121: Update FallThrough::route to validate score.target with
ensure_model_is_target against driver.models_for(Category::Any) before decision
replay and RoutingOutcome construction; propagate the validation error and
preserve the existing fallback routing behavior.

In `@crates/libsy/src/algorithms/rand.rs`:
- Line 42: Validate the configured weight count against options.len() before
constructing the distribution or sampling indices in RandomClassifier. Return
LibsyError::AlgorithmError when the counts differ, while preserving the existing
behavior for matching counts and uniform sampling.

In `@crates/libsy/src/algorithms/util/affinity.rs`:
- Around line 252-260: Move the Driver::set_evidence call that records
"retained" until after the assignment availability check in the
assignment-resolution flow, so it runs only when the assignment survives and is
returned. Preserve eviction behavior for unavailable models, and add a test
verifying an evicted assignment produces no retained evidence.

In `@crates/libsy/src/algorithms/util/llm_judge.rs`:
- Around line 356-361: The custom classifier route setup must reject
configurations with an empty Category::Judge model list before constructing or
invoking JudgeClassifier. Add validation for custom routes that require at least
one judge model, while preserving the existing no-model error behavior and
leaving capability/escalation routes unchanged.

In `@crates/libsy/src/algorithms/util/target_selector.rs`:
- Around line 49-53: Update TargetSelectorPolicy’s category classification
branch to check models_for(category) before selecting a model; return
Classification::Ambiguous for parseable categories with no mapped models instead
of propagating first_model_for errors, allowing FallThrough to reach
DefaultCategoryClassifier. Add a test covering an unmapped category and
verifying the default target is used.

In `@crates/switchyard-runner/src/algorithm.rs`:
- Around line 476-479: Update custom-mode handling in
SubagentRouteConfig::routing_target_names to derive only completion targets,
excluding judge-only names rather than using CategoryModelConfig::all_names.
Update callable_target_names to append the custom mode’s judge names so judge
calls still receive clients while routing consumers never treat judges as
completion destinations.
- Around line 659-666: Update merge_category_models to deduplicate model names
while merging each category, preserving their first-seen order so repeated
parent and sub-agent targets appear only once.

In `@crates/switchyard-server/src/lib.rs`:
- Line 197: Update the ServerState::new call to pass the runtime
category-to-model map instead of HashMap::new(), ensuring each Route receives
the models used by Route::execute and Passthrough. Change the constructor and
relevant state initialization to accept and retain this map, without deriving it
from ClientRouter.

In `@README.md`:
- Line 174: Update the README algorithm example around algorithm.run_stream so
it passes the request-time category-to-model mapping described earlier. Adjust
the surrounding example as needed to define or obtain that runtime model
catalog, while preserving the existing request execution flow.

---

Nitpick comments:
In `@crates/switchyard-py/src/libsy_bindings.rs`:
- Around line 647-652: Document the runtime category mapping consistently in
PyAlgorithm::run_stream, Algorithm.run_stream, and
SwitchyardRoutingPlugin.models, covering any, judge, capable, and efficient,
their algorithm-specific candidate requirements, unknown-category ValueError
behavior, plugin defaults, and candidate-pool invariant; align wording with the
existing TOML reference.

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