fix(backend): 修复全面审阅发现的核心问题

修复索引首次失败回滚、Vault 扫描边界、Markdown 代码围栏和 UTF-16 Citation 偏移。

收紧 Plugin 权限与 JSON Schema 校验，补齐 Note Move、Task、Attachment 和 Transcript Tool。

接入 OpenAI SSE 与 Ollama JSONL 真流式输出，修正 Provider PATCH 语义并限制运行时内存保留。

新增对应回归测试，后端测试增至 62 项。

backend/app/services/index_service.py

@@ -17,11 +17,24 @@ from app.contracts import IndexJob, IndexRebuildRequest, IndexStatus
 from app.errors import ApiError
 from app.knowledge.parser import parse_note
 from app.services.note_service import index_note
+from app.services import task_service
+from app.services.coordination import serialized_vault_mutation
 from app.retrieval.vectorstore import SqliteVecStore
 
 vector_store = SqliteVecStore()
 
 _jobs: dict[str, IndexJob] = {}
+_active_job_id: str | None = None
+_last_completed_at: datetime | None = None
+_last_error: str | None = None
+MAX_JOBS = 100
+
+
+def _remember_job(job: IndexJob) -> None:
+    _jobs[job.job_id] = job
+    while len(_jobs) > MAX_JOBS:
+        oldest = next(iter(_jobs))
+        _jobs.pop(oldest, None)
 
 
 def _scan_vault() -> list[tuple[str, str, str, datetime, datetime]]:
@@ -29,23 +42,28 @@ def _scan_vault() -> list[tuple[str, str, str, datetime, datetime]]:
 
     先读入内存：若文件读取失败，rebuild 尚未清空旧索引，不会造成数据损失。
     """
-    vault = get_settings().vault_path
+    vault = get_settings().vault_path.resolve()
     result: list[tuple[str, str, str, datetime, datetime]] = []
     if not vault.exists():
         return result
     for path in sorted(vault.rglob("*.md")):
+        resolved = path.resolve()
+        if not resolved.is_relative_to(vault):
+            continue
         rel = path.relative_to(vault).as_posix()
         folder = path.relative_to(vault).parent.as_posix()
         if folder == ".":
             folder = ""
-        stat = path.stat()
+        stat = resolved.stat()
         created = datetime.fromtimestamp(stat.st_ctime, tz=timezone.utc)
         updated = datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc)
-        result.append((rel, folder, path.read_text(encoding="utf-8"), created, updated))
+        result.append((rel, folder, resolved.read_text(encoding="utf-8"), created, updated))
     return result
 
 
+@serialized_vault_mutation
 async def rebuild(request: IndexRebuildRequest) -> IndexJob:
+    global _active_job_id, _last_completed_at, _last_error
     job_id = "job_" + uuid4().hex[:12]
     # 增量重建（scope != all 或指定 note_ids）尚未实现，明确拒绝而非静默全量重建
     if request.scope != "all" or request.note_ids:
@@ -59,10 +77,22 @@ async def rebuild(request: IndexRebuildRequest) -> IndexJob:
     # 先扫描到内存（失败不会清旧索引），再快照旧库用于失败回滚
     docs = _scan_vault()
     settings = get_settings()
-    backup_path = settings.db_path.with_suffix(".db.bak") if settings.db_path.exists() else None
+    database_existed = settings.db_path.exists()
+    task_note_links = task_service.note_links() if database_existed else {}
+    backup_path = (
+        settings.db_path.with_name(f"{settings.db_path.name}.{job_id}.bak")
+        if database_existed
+        else None
+    )
     if backup_path is not None:
         shutil.copy2(settings.db_path, backup_path)
 
+    _active_job_id = job_id
+    _last_error = None
+    _remember_job(IndexJob(
+        job_id=job_id, status="running", scope=request.scope,
+        created_at=datetime.now(timezone.utc),
+    ))
     try:
         repository.clear_all()
         await vector_store.clear()
@@ -72,27 +102,39 @@ async def rebuild(request: IndexRebuildRequest) -> IndexJob:
                 created_at=created, updated_at=updated,
             )
             await index_note(parsed)
-    except BaseException:
+        task_service.restore_note_links(task_note_links)
+    except BaseException as exc:
         # 重建失败：恢复旧索引，避免留下半成品；记录 failed 任务后向上抛
         if backup_path is not None and backup_path.exists():
             shutil.copy2(backup_path, settings.db_path)
-        _jobs[job_id] = IndexJob(
+        elif not database_existed:
+            settings.db_path.unlink(missing_ok=True)
+        _remember_job(IndexJob(
             job_id=job_id, status="failed", scope=request.scope,
             created_at=datetime.now(timezone.utc),
-        )
+        ))
+        _last_error = str(exc)
         raise
     finally:
+        _active_job_id = None
         if backup_path is not None:
             backup_path.unlink(missing_ok=True)
 
     job = IndexJob(job_id=job_id, status="completed", scope=request.scope, created_at=datetime.now(timezone.utc))
-    _jobs[job_id] = job
+    _remember_job(job)
+    _last_completed_at = job.created_at
     return job
 
 
 def get_status() -> IndexStatus:
-    # 同步重建、无排队任务，因此状态恒为 idle；实际索引规模可由 GET /api/notes 与搜索反映
-    return IndexStatus(status="idle", pending_jobs=0)
+    if _active_job_id is not None:
+        return IndexStatus(status="running", pending_jobs=0, active_job_id=_active_job_id)
+    return IndexStatus(
+        status="failed" if _last_error else "idle",
+        pending_jobs=0,
+        last_completed_at=_last_completed_at,
+        error_message=_last_error,
+    )
 
 
 def get_job(job_id: str) -> IndexJob | None: