docs: detail per-agent prompt caching configuration

docs/concepts/session-pruning.md

@@ -15,13 +15,13 @@ Session pruning trims **old tool results** from the in-memory context right befo
 - When `mode: "cache-ttl"` is enabled and the last Anthropic call for the session is older than `ttl`.
 - Only affects the messages sent to the model for that request.
 - Only active for Anthropic API calls (and OpenRouter Anthropic models).
-- For best results, match `ttl` to your model `cacheControlTtl`.
+- For best results, match `ttl` to your model `cacheRetention` policy (`short` = 5m, `long` = 1h).
 - After a prune, the TTL window resets so subsequent requests keep cache until `ttl` expires again.
 
 ## Smart defaults (Anthropic)
 
 - **OAuth or setup-token** profiles: enable `cache-ttl` pruning and set heartbeat to `1h`.
-- **API key** profiles: enable `cache-ttl` pruning, set heartbeat to `30m`, and default `cacheControlTtl` to `1h` on Anthropic models.
+- **API key** profiles: enable `cache-ttl` pruning, set heartbeat to `30m`, and default `cacheRetention: "short"` on Anthropic models.
 - If you set any of these values explicitly, OpenClaw does **not** override them.
 
 ## What this improves (cost + cache behavior)
@@ -91,9 +91,7 @@ Default (off):
 
 ```json5
 {
-  agent: {
-    contextPruning: { mode: "off" },
-  },
+  agents: { defaults: { contextPruning: { mode: "off" } } },
 }
 ```
 
@@ -101,9 +99,7 @@ Enable TTL-aware pruning:
 
 ```json5
 {
-  agent: {
-    contextPruning: { mode: "cache-ttl", ttl: "5m" },
-  },
+  agents: { defaults: { contextPruning: { mode: "cache-ttl", ttl: "5m" } } },
 }
 ```
 
@@ -111,10 +107,12 @@ Restrict pruning to specific tools:
 
 ```json5
 {
-  agent: {
-    contextPruning: {
-      mode: "cache-ttl",
-      tools: { allow: ["exec", "read"], deny: ["*image*"] },
+  agents: {
+    defaults: {
+      contextPruning: {
+        mode: "cache-ttl",
+        tools: { allow: ["exec", "read"], deny: ["*image*"] },
+      },
     },
   },
 }