docs: README coverage for resolvers, DefineTool, agent hooks, ops controls

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -79,6 +79,16 @@ Aliases may appear anywhere in a chain (head, middle, tail), may reference
 other aliases, and expand inline and recursively; cycles are detected and
 returned as errors.
 
+For tiers that live in a database or config system, register a **dynamic
+resolver** — consulted after static aliases, output expanded with the same
+recursion and cycle guards:
+
+```go
+reg.RegisterResolver(majordomo.ResolverFunc(func(name string) (string, bool) {
+    return myConfigStore.LookupTier(name) // e.g. "agent-thinking" → a chain
+}))
+```
+
 ### Failover & health
 
 Chains are health-tracked per target:
@@ -93,6 +103,9 @@ Chains are health-tracked per target:
   configurable via `WithChainConfig` / `WithHealthConfig`.
 - If every element fails, you get one joined error naming each target and
   why it failed.
+- Ops surfaces: `reg.Health()` exposes `Bench`/`Unbench`/`Snapshot` for
+  manual control and dashboards; `ChainConfig.Observer` receives one event
+  per failover decision (failed attempt, bench, benched-skip) for logging.
 
 ## Providers
 
@@ -188,6 +201,17 @@ resp, _ := m.Generate(ctx, req, majordomo.WithTools(weather))
 // resp.ToolCalls → execute → append ToolResultsMessage → continue
 ```
 
+Or typed, with the schema derived from your argument struct:
+
+```go
+weather := majordomo.DefineTool("get_weather", "Current weather for a city",
+    func(ctx context.Context, args struct {
+        City string `json:"city" description:"city name"`
+    }) (any, error) {
+        return lookup(args.City)
+    })
+```
+
 Each provider maps this one shape to its native function-calling format
 (OpenAI tools/tool_calls, Anthropic tool_use/tool_result, Ollama tools with
 object arguments). Tool-call ids are synthesized when a backend omits them;
@@ -237,6 +261,13 @@ the model can react to; unknown tools likewise; duplicate tool names across
 toolboxes fail loudly. On `agent.ErrMaxSteps` (and on model errors) the
 partial result with the full transcript is still returned.
 
+Supervision hooks for orchestrators: `WithMaxStepsFunc` (dynamic step
+budget), `WithSteer` (inject messages into a running agent),
+`WithCompactor` (transform the outbound transcript when context grows —
+the canonical `Result.Messages` stays complete), and `WithToolErrorLimits`
+(circuit breakers for all-error steps and identical repeated calls,
+surfacing `agent.ErrToolLoop`).
+
 ## Skills
 
 Skills are reusable instruction+tool bundles attachable to **any** agent,