fix(recovery): restore compaction pipeline sufficient check and conservative charsPerToken

Fixes critical v2.10.0 compaction regression where truncation ALWAYS returned early
without checking if it was sufficient, causing PHASE 3 (Summarize) to be skipped.
This led to "history disappears" symptom where all context was lost after compaction.

Changes:
- Restored aggressiveResult.sufficient check before early return in executor
- Only return from Truncate phase if truncation successfully reduced tokens below limit
- Otherwise fall through to Summarize phase when truncation is insufficient
- Restored conservative charsPerToken=4 (was changed to 2, too aggressive)
- Added 2 regression tests:
  * Test 1: Verify Summarize is called when truncation is insufficient
  * Test 2: Verify Summarize is skipped when truncation is sufficient

Regression details:
- v2.10.0 changed charsPerToken from 4 to 2, making truncation too aggressive
- Early return removed sufficient check, skipping fallback to Summarize
- Users reported complete loss of conversation history after compaction

🤖 Generated with assistance of OhMyOpenCode (https://github.com/code-yeongyu/oh-my-opencode)

src/hooks/anthropic-context-window-limit-recovery/executor.ts

@@ -401,21 +401,31 @@ export async function executeCompact(
 
         log("[auto-compact] aggressive truncation completed", aggressiveResult);
 
-        clearSessionState(autoCompactState, sessionID);
-        setTimeout(async () => {
-          try {
-            await (client as Client).session.prompt_async({
-              path: { sessionID },
-              body: { parts: [{ type: "text", text: "Continue" }] },
-              query: { directory },
-            });
-          } catch {}
-        }, 500);
-        return;
+        // Only return early if truncation was sufficient to get under token limit
+        // Otherwise fall through to PHASE 3 (Summarize)
+        if (aggressiveResult.sufficient) {
+          clearSessionState(autoCompactState, sessionID);
+          setTimeout(async () => {
+            try {
+              await (client as Client).session.prompt_async({
+                path: { sessionID },
+                body: { parts: [{ type: "text", text: "Continue" }] },
+                query: { directory },
+              });
+            } catch {}
+          }, 500);
+          return;
+        }
+        // Truncation was insufficient - fall through to Summarize
+        log("[auto-compact] truncation insufficient, falling through to summarize", {
+          sessionID,
+          truncatedCount: aggressiveResult.truncatedCount,
+          sufficient: aggressiveResult.sufficient,
+        });
       }
     }
 
-    // PHASE 3: Summarize - fallback when no tool outputs to truncate
+    // PHASE 3: Summarize - fallback when truncation insufficient or no tool outputs
     const retryState = getOrCreateRetryState(autoCompactState, sessionID);
 
     if (errorData?.errorType?.includes("non-empty content")) {