2b GC follow-on: drop dead CpSharedL2NodeMetadata.{committed, committed_payload_layers}

Tier-2-GC follow-on (design §9.12 flagged vestige). The metadata's `committed`
bool and `committed_payload_layers` dict were write-only residue of the option-A
quorum the GC removed: set at construction, validated in __post_init__, copied in
split() -- but their only content/True writer was the deleted
_commit_cp_shared_l2_layers_batched. Verified tree-wide there is NO live reader
(`committed` appears only in split's `committed=self.committed` copy;
`committed_payload_layers` only in __post_init__ validation + split copy +
construction). Commit consensus under B1 is the allocator's `_committed_objects`
(MIN frontier), so `metadata.committed` was a redundant second source of truth.

CORRECTION to the original flag: `required_payloads` is NOT a vestige -- it is
LIVE (read by cache_controller.load_cp_shared_l2, the evict path hiradix:2748,
and the readback payload planning). KEPT.

Removed: the 2 dataclass fields + their __post_init__ validation + the two split()
child-copies + the cache_controller reserve-construction kwargs + 4 test
constructions/assertions. No behavior change (fields were never read). Pool suite
88/88 (syh-dev-new/torch-2.11 env) + import smoke confirm the metadata dataclass is
now {logical_len, padded_len, page_size, object_ranges, required_payloads, object_key}.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

python/sglang/srt/managers/cache_controller.py

@@ -1412,8 +1412,6 @@ class HiCacheController:
                 page_size=page_size,
                 object_ranges=object_ranges,
                 required_payloads=tuple(required_payloads),
-                committed_payload_layers={payload: set() for payload in required_payloads},
-                committed=False,
                 object_key=object_key,
             )
             return HiCacheWriteReservation(

python/sglang/srt/mem_cache/cp_shared_l2_pool.py

@@ -438,8 +438,6 @@ class CpSharedL2NodeMetadata:
     page_size: int
     object_ranges: dict[str, CpSharedL2ObjectRange]
     required_payloads: tuple[str, ...]
-    committed_payload_layers: dict[str, set[int]]
-    committed: bool = False
     object_key: str = ""
 
     def __post_init__(self):
@@ -466,13 +464,6 @@ class CpSharedL2NodeMetadata:
                     f"payload_kind={object_range.payload_kind!r}"
                 )
 
-        for payload_kind, layers in self.committed_payload_layers.items():
-            self._validate_payload_kind(payload_kind)
-            if not isinstance(layers, set):
-                raise ValueError("committed_payload_layers values must be sets")
-            if any(layer < 0 for layer in layers):
-                raise ValueError("committed payload layer ids must be non-negative")
-
     @staticmethod
     def _validate_payload_kind(payload_kind: str):
         if payload_kind not in _VALID_PAYLOAD_KINDS:
@@ -533,10 +524,6 @@ class CpSharedL2NodeMetadata:
                 generation=object_range.generation,
             )
 
-        committed_layers = {
-            payload_kind: set(layers)
-            for payload_kind, layers in self.committed_payload_layers.items()
-        }
         return (
             CpSharedL2NodeMetadata(
                 logical_len=split_len,
@@ -544,11 +531,6 @@ class CpSharedL2NodeMetadata:
                 page_size=self.page_size,
                 object_ranges=parent_ranges,
                 required_payloads=tuple(self.required_payloads),
-                committed_payload_layers={
-                    payload_kind: set(layers)
-                    for payload_kind, layers in committed_layers.items()
-                },
-                committed=self.committed,
                 object_key=parent_key,
             ),
             CpSharedL2NodeMetadata(
@@ -557,11 +539,6 @@ class CpSharedL2NodeMetadata:
                 page_size=self.page_size,
                 object_ranges=child_ranges,
                 required_payloads=tuple(self.required_payloads),
-                committed_payload_layers={
-                    payload_kind: set(layers)
-                    for payload_kind, layers in committed_layers.items()
-                },
-                committed=self.committed,
                 object_key=child_key,
             ),
         )