fix(l2): reconcile fs-native eviction ledger drift

[yatesdr]

What this PR does / why we need it:

fs_native returned a false per-key delete result when an object was already
absent. NativeConnectorL2Adapter consequently retained that key's byte
accounting and LRU entry forever, causing repeated no-op eviction and eventual
store admission failures. A concurrent re-store could create this state because
L2 eviction did not protect keys with pending native store completions.

This change makes native filesystem deletion idempotent for an already-absent
object while preserving filesystem errors, and excludes pending-store keys from
adapter deletion. Regression tests cover both ledger reconciliation and the
store/delete completion race.

Special notes for your reviewers:

Reproduced on cn4 with qualified image
localinferencelab/vllm@sha256:c9ad4a6ef4aa55232df9ed1a37e85d94eb8c7d5349561a6cbe828e72b61de83c
(LMCache 35ad809f): after removing a tracked payload, two deletes left the
20-byte ledger entry and key tracking unchanged.

Validation:

• Rebuilt LMCache with NO_GPU_EXT=1 in the qualified r32 environment.
• 108 tests passed across test_native_connector_l2_adapter.py and
  test_fs_native_connector.py.
• Focused Ruff lint/format, mypy, and clang-format checks passed.
• GitHub Code Quality, CodeQL, and CPU artifact build checks pass.

Current unrelated dev CI failures:

• The full Python 3.11 run completes 5,803 tests and fails one unchanged
  multiprocess test because its _FakeStorageManager lacks the existing
  abort_write method; the remaining Python matrix jobs are then cancelled.
• All four CPU-device jobs install the current vLLM nightly and fail in the
  unchanged vLLM integration path because KVConnectorBlockState.block_ids
  has been replaced by get_block_ids.

CodeRabbit reports success but skips automatic review because this OSS
repository has fewer than ten stars and therefore requires a manual review
trigger.

If applicable:

• this PR contains user facing changes - docs added
• this PR contains unit tests

[coderabbitai]

Important

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Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: a42816c1-1098-4cb3-af58-3df8837000d9

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[voipmonitor]

Independent validation of the filesystem eviction-ledger fix on the shared GLM/Qwen/DS4 serving image:

• Exact R32 reproduces the absent-file deletion failure for both short and bounded long keys. The adapter retains stale byte/LRU accounting when the file is already absent.
• With both commits from this PR, 116 installed-image connector/adapter tests pass, including absent-file deletion, pending-store eviction exclusion and actual filesystem-error propagation. A nonempty-directory delete still fails without retiring its accounting.
• TP4/DCP1 MTP3 with FP8 KV, a 4096-token scheduler budget, 4 GiB RAM tier and fs_native passes exact 54,641-token cold/GPU/RAM/filesystem/restart checks. RAM restore is 0.260 s, filesystem restore 0.277 s and restore after restarting workers plus sidecar 0.414 s. All restores recompute zero prompt tokens. Shared SYSTEM reuse and changed-SYSTEM isolation pass too. Filesystem timings include a warm OS page cache.

The integration preserves R32's bounded long-key paths and legacy-path cleanup: every representable path is processed, missing files count as successful deletion, and genuine I/O errors propagate. The CPU filesystem extension is rebuilt; all audited CUDA/vLLM/FlashKDA binaries remain byte-identical. The sidecar remains CPU-only and GPU copies stay worker-owned.

Complete attributed integration preserves Derek Yates's two commits with source-commit references. This PR remains the canonical review unit; no duplicate PR was created. Scope is filesystem-ledger correctness and a bounded GLM transport regression check, not fresh TP8, NVFP4-KV or Qwen/DS4 external-cache qualification.

[voipmonitor]

Superseded by #49, which now preserves Derek Yates’s filesystem eviction-ledger commits together with bounded cache-key paths. The audited #67 head ec09897 is an ancestor of #49 head b4b79a0. Canonical and legacy files must both be absent before retiring ledger accounting; missing files are idempotent and actual deletion errors retain the ledger. The affected native implementation matches the published R34 source, and 116 filesystem/native-adapter tests pass. Closing this separate review unit avoids stacking two overlapping filesystem lifecycle patches; contribution credit and Git history remain intact.