test(catalog): expand agents to 10 tests per subcategory

Bring agents/tool-routing and agents/planning up to 10 tests each.
Add a new agents/delegation subcategory with 10 tests. Split
agents.go into agents_toolrouting.go, agents_planning.go, and
agents_delegation.go, each with a sibling _test.go file, and reduce
agents.go to a thin registration aggregator.

Every new prompt is self-contained and forces a JSON or number-only
answer. Set-valued answers use JSONStringSet or a custom stage-set
evaluator so no arbitrary order is required. Dependency-graph fixtures
that force a single valid order are verified unique in the unit tests
by brute-force enumeration over every permutation. Numeric ground
truth is derived by running the same algorithm the fixture describes,
then cross-checked against an independently hand-derived value.

MaxTokens is omitted on all 28 new tests per the expansion rules; the
2 existing tests keep their prior value unchanged.

internal/tests/agents.go

@@ -1,106 +1,14 @@
 package tests
 
-import (
-	"github.com/lukaszraczylo/llm-testbench/internal/eval"
-	"github.com/lukaszraczylo/llm-testbench/internal/testkit"
-)
+import "github.com/lukaszraczylo/llm-testbench/internal/testkit"
 
+// registerAgentsTests registers every agents-category test. Each
+// subcategory - tool-routing, planning, and delegation - has its own
+// register function and source file (agents_toolrouting.go,
+// agents_planning.go, agents_delegation.go) to keep any one file from
+// growing past a few hundred lines.
 func registerAgentsTests(r *testkit.Registry) {
-	r.Register(agentToolRoutingTest())
-	r.Register(agentPlanOrderingTest())
-}
-
-// agentToolRoutingRoster is the inline tool roster for
-// agentToolRoutingTest.
-const agentToolRoutingRoster = `- search_web: Search the public web for current information not in your
-  training data.
-- read_file: Read the contents of a file from the local filesystem.
-- run_shell: Execute an arbitrary shell command on the local machine.
-- query_db: Run a read-only SQL query against the application's Postgres
-  database.
-- send_email: Send an email to a specified recipient.
-- none: No tool is needed; answer directly from what you already know.`
-
-// agentToolRoutingTest: map 4 mini-tasks to the correct tool from a 6-tool
-// roster.
-//
-// ground truth: task1 is arithmetic answerable without any tool (none);
-// task2 needs a row count from a database table (query_db); task3 asks for
-// current information that cannot be in training data (search_web); task4
-// asks to notify someone by email (send_email).
-func agentToolRoutingTest() testkit.Test {
-	prompt := `You have access to this roster of tools:
-
-` + agentToolRoutingRoster + `
-
-For each of these 4 tasks, decide which single tool (or "none") is the
-correct one to use:
-
-task1: "What is 15% of 240?"
-task2: "How many rows are in the 'orders' table?"
-task3: "What is today's top headline on a major news site?"
-task4: "Notify the on-call engineer at [email protected] that the deploy
-finished."
-
-Respond with only a JSON object mapping each task id to the tool name:
-{"task1":"...","task2":"...","task3":"...","task4":"..."}`
-
-	evaluator := eval.Mean(
-		eval.JSONField("task1", "none"),
-		eval.JSONField("task2", "query_db"),
-		eval.JSONField("task3", "search_web"),
-		eval.JSONField("task4", "send_email"),
-	)
-
-	return testkit.Test{
-		ID:          "agent-tool-routing",
-		Category:    "agents",
-		Subcategory: "tool-routing",
-		Description: "Map 4 mini-tasks to the correct tool from a 6-tool roster.",
-		Prompt:      prompt,
-		MaxTokens:   300,
-		Eval:        evaluator,
-	}
-}
-
-// agentPlanOrderingWant is the unique valid step order implied by the
-// dependency constraints in agentPlanOrderingTest's prompt.
-var agentPlanOrderingWant = []string{"build", "test", "backup", "deploy", "verify", "rollback"}
-
-// agentPlanOrderingTest: order deployment steps that have explicit
-// pairwise dependencies.
-//
-// ground truth: the prompt states build must precede test (need a built
-// artifact to test), backup must happen only after tests pass and only
-// before deploy, deploy must follow backup, verify must follow deploy, and
-// rollback is only meaningful after a deploy whose verify step failed. This
-// pins a single valid total order: build, test, backup, deploy, verify,
-// rollback.
-func agentPlanOrderingTest() testkit.Test {
-	prompt := `You are planning a deployment with these steps: build, test,
-backup, deploy, verify, rollback.
-
-Constraints:
-- You must build the artifact before you can test it.
-- You only take a backup of the current production state once tests have
-  passed - there is no point backing up before you know the new build is
-  viable.
-- Deploy only happens after the backup completes.
-- After deploy, you must verify the new deployment is healthy.
-- Rollback (restoring the pre-deploy backup) only makes sense after a
-  deploy has happened, and only if verify fails.
-
-Give the single correct step order as a JSON array of step ids, e.g.
-["build","test",...]. Include all 6 steps, listing rollback in its position
-in the sequence even though it is conditional on verify failing.`
-
-	return testkit.Test{
-		ID:          "agent-plan-ordering",
-		Category:    "agents",
-		Subcategory: "planning",
-		Description: "Order 6 deployment steps under explicit pairwise dependency constraints.",
-		Prompt:      prompt,
-		MaxTokens:   300,
-		Eval:        eval.JSONStringArrayEquals(agentPlanOrderingWant),
-	}
+	registerAgentToolRoutingTests(r)
+	registerAgentPlanningTests(r)
+	registerAgentDelegationTests(r)
 }