fix(token_optimizer): include content in CacheEntry.to_dict — closes #770 cache-loss defect

Pre-fix to_dict omitted the required field content, so _load's
CacheEntry(**entry_data) raised TypeError on every reload and the
blanket except silently discarded the whole cache on every restart.

Frozen regression contract tests/test_token_optimizer_cache.py
(3 tests: save_persists_content, roundtrip_restores_content,
corrupt_storage_degrades_to_empty_cache). Full suite 2250/0.

src/rune/token_optimizer.py

@@ -44,8 +44,13 @@ class CacheEntry:
     hit_count: int = 0
 
     def to_dict(self):
+        # `content` is required by CacheEntry; omitting it here made the
+        # persisted JSON unloadable (CacheEntry(**entry_data) raised on
+        # _load), which the blanket except in _load turned into silent
+        # total cache loss on every restart. See issue #770.
         return {
             "key": self.key,
+            "content": self.content,
             "tokens": self.tokens,
             "last_used": self.last_used,
             "use_count": self.use_count,

tests/test_token_optimizer_cache.py

@@ -0,0 +1,62 @@
+"""Cache roundtrip contract for TokenOptimizer.
+
+Rebase w2 disposition evidence for issue #770: CacheEntry.to_dict omitted
+`content`, so the persisted JSON could never satisfy CacheEntry(**entry_data)
+on _load — the blanket except in _load silently discarded the whole cache on
+every process restart. These tests freeze the repaired contract.
+"""
+
+import json
+
+from rune.token_optimizer import CacheEntry, TokenOptimizer
+
+
+def _entry(key: str = "static", content: str = "constitution text") -> CacheEntry:
+    return CacheEntry(
+        key=key,
+        content=content,
+        tokens=4,
+        last_used="2026-01-01T00:00:00+00:00",
+        use_count=1,
+        hit_count=0,
+    )
+
+
+def _seed(opt: TokenOptimizer, key: str = "static", content: str = "constitution text"):
+    """Seed a cache entry via the real mutation contract (every mutator
+    pairs its change with _mark_dirty — direct assignment alone never
+    reaches the save path)."""
+    opt.cache[key] = _entry(key, content)
+    opt._mark_dirty()
+    return opt
+
+
+def test_save_persists_content(tmp_path):
+    path = tmp_path / "tok.json"
+    opt = TokenOptimizer(storage_path=str(path))
+    _seed(opt)
+    opt.flush()
+
+    data = json.loads(path.read_text())
+    assert data["cache"]["static"]["content"] == "constitution text"
+
+
+def test_roundtrip_restores_content(tmp_path):
+    path = str(tmp_path / "tok.json")
+    seeder = TokenOptimizer(storage_path=path)
+    _seed(seeder)
+    seeder.flush()
+
+    reloaded = TokenOptimizer(storage_path=path)
+    assert "static" in reloaded.cache
+    assert reloaded.cache["static"].content == "constitution text"
+    assert reloaded.cache["static"].tokens == 4
+
+
+def test_corrupt_storage_degrades_to_empty_cache(tmp_path):
+    """The blanket except in _load is a deliberate corrupt-file recovery path:
+    the optimizer must start empty, never crash."""
+    path = tmp_path / "tok.json"
+    path.write_text("{not json at all")
+    opt = TokenOptimizer(storage_path=str(path))
+    assert opt.cache == {}