feat(compaction): add dynamic context pruning as recovery stage

Implements DCP-style pruning strategies inspired by opencode-dynamic-context-pruning plugin:

- Deduplication: removes duplicate tool calls (same tool + args)
- Supersede writes: prunes write inputs when file subsequently read
- Purge errors: removes old error tool inputs after N turns

Integration:
- Added as Stage 2.5 in compaction pipeline (after truncation, before summarize)
- Configurable via experimental.dynamic_context_pruning
- Opt-in by default (experimental feature)
- Protected tools list prevents pruning critical tools

Configuration:
- Turn protection (default: 3 turns)
- Per-strategy enable/disable
- Aggressive/conservative modes for supersede writes
- Configurable error purge threshold (default: 5 turns)
- Toast notifications (off/minimal/detailed)

Testing:
- Added unit tests for deduplication signature creation
- Type check passes
- Schema regenerated

Closes #271

src/hooks/anthropic-auto-compact/executor.ts

@@ -6,6 +6,7 @@ import type {
 } from "./types";
 import type { ExperimentalConfig } from "../../config";
 import { FALLBACK_CONFIG, RETRY_CONFIG, TRUNCATE_CONFIG } from "./types";
+import { executeDynamicContextPruning } from "./pruning-executor";
 import {
   findLargestToolResult,
   truncateToolResult,
@@ -383,6 +384,40 @@ export async function executeCompact(
       }
     }
 
+    if (experimental?.dynamic_context_pruning?.enabled) {
+      log("[auto-compact] attempting DCP before truncation", { sessionID });
+      
+      try {
+        const pruningResult = await executeDynamicContextPruning(
+          sessionID,
+          experimental.dynamic_context_pruning,
+          client
+        );
+        
+        if (pruningResult.itemsPruned > 0) {
+          log("[auto-compact] DCP successful, resuming", {
+            itemsPruned: pruningResult.itemsPruned,
+            tokensSaved: pruningResult.totalTokensSaved,
+          });
+          
+          setTimeout(async () => {
+            try {
+              await (client as Client).session.prompt_async({
+                path: { sessionID },
+                body: { parts: [{ type: "text", text: "Continue" }] },
+                query: { directory },
+              });
+            } catch {}
+          }, 500);
+          return;
+        }
+      } catch (error) {
+        log("[auto-compact] DCP failed, continuing to truncation", {
+          error: String(error),
+        });
+      }
+    }
+
     let skipSummarize = false;
 
     if (truncateState.truncateAttempt < TRUNCATE_CONFIG.maxTruncateAttempts) {