Give each tracker agent its own config

The tracker-mapping, common-pattern enrichment, and third-party
disambiguation agents were all built from one shared
TrackerAgentsConfig fed by a single tracker-mapping config slot. That
forced a single AgentTimeout to be reused and patched per worker, and
two unrelated max-turns fields to share one struct.

Split the in-code config into TrackerMappingAgentConfig,
TrackerEnrichmentAgentConfig, and DisambiguationAgentConfig, each with
its own timeout and max-turns, and add dedicated tracker-enrichment and
third-party-disambiguation provider slots (the latter resolving next to
third-party-vetter). Enrichment and disambiguation fall back to the
tracker-mapping slot when their own provider is unset, preserving
single-config deployments.

Drop the shared pkg/agentsbuild package and duplicate its small wiring
into probod and proboctl so the two executables stay decoupled. Wire
the new env vars, builder test coverage, and Helm values.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/thirdparty/disambiguation_agent.go

@@ -54,7 +54,7 @@ const (
 	defaultDisambiguationMaxTokens = 4096
 )
 
-// DisambiguationConfig configures the third-party disambiguation
+// DisambiguationAgentConfig configures the third-party disambiguation
 // agent. The agent has no DB tools and no web-search tools: the
 // candidate list is supplied entirely in the prompt and the agent
 // only picks among it.
@@ -62,7 +62,7 @@ const (
 // MaxTokens and Temperature bound and steer the single LLM call, and
 // Timeout caps a single run. Zero-valued fields fall back to package
 // defaults.
-type DisambiguationConfig struct {
+type DisambiguationAgentConfig struct {
 	LLMClient   *llm.Client
 	Model       string
 	MaxTokens   *int
@@ -84,7 +84,7 @@ type DisambiguationResult struct {
 // no tools: the candidate list is supplied in the prompt and the
 // agent must only choose among it.
 func BuildDisambiguationAgent(
-	cfg DisambiguationConfig,
+	cfg DisambiguationAgentConfig,
 	logger *log.Logger,
 ) *agent.Agent {
 	outputType, err := agent.NewOutputType[DisambiguationResult]("third_party_disambiguation")