升级Trellis并精简项目知识（09-05-trellis-upgrade-rule-cleanup）

更新Trellis适配、任务归属与归档失败恢复，精简技能入口和知识读取规则。
保留权限、证据、事务及独立复核合同；纳入对应任务及已完成复核记录。
仅本地提交，不启用新平台适配，不推送或部署。

.trellis/scripts/common/active_task.py

@@ -648,17 +648,15 @@ def resolve_active_task(
     platform_input: dict[str, Any] | None = None,
     platform: str | None = None,
     *,
-    allow_single_session_fallback: bool = True,
+    allow_single_session_fallback: bool = False,
     allow_environment_context: bool = True,
 ) -> ActiveTask:
     """Resolve the active task from session runtime state only.
 
     A stale session task is returned as stale. Missing context identity or a
-    missing/empty session context falls back to single-session inference: if
-    exactly one session file exists in the runtime, return its task with
-    source_type="session-fallback" — covers pull-based platform sub-agents
-    (copilot, gemini, qoder) that don't inherit the parent's session id. ≥2
-    files or 0 files yield ActiveTask(None) — refuses to guess across windows.
+    Missing or unmatched session identity does not infer ownership from the
+    number of session files. Pull-based child-agent callers that cannot inherit
+    a parent identity must opt into the compatibility fallback explicitly.
     """
     context_key = resolve_context_key(
         platform_input,

.trellis/scripts/common/task_store.py

@@ -196,6 +196,40 @@ def _report_write_failure(path: Path) -> None:
     )
 
 
+def _restore_child_links(unlinked: dict[Path, str | None]) -> None:
+    """Put back the parent links this archive attempt already removed.
+
+    The unlink loop below walks a parent's children one at a time, so a
+    failure part-way through leaves the earlier children carrying
+    ``parent: null`` while their parent is still in the active tree. That is
+    the mirror image of the dangling reference the same loop already refuses
+    to create, and nothing repairs it later either, so undo it before the
+    failure is reported.
+
+    Restoring is best-effort: if a child cannot be written back, name it so
+    the caller can re-link it by hand instead of guessing which one broke.
+    """
+    broken: list[str] = []
+    for child_json, original_parent in unlinked.items():
+        child_data, _ = read_json_checked(child_json)
+        if child_data is None:
+            broken.append(child_json.parent.name)
+            continue
+        child_data["parent"] = original_parent
+        if not write_json(child_json, child_data):
+            broken.append(child_json.parent.name)
+    if broken:
+        print(
+            colored(
+                f"Warning: could not restore the parent link on: {', '.join(broken)}. "
+                "Re-link each one with `python3 .trellis/scripts/task.py "
+                "add-subtask <parent> <child>`.",
+                Colors.RED,
+            ),
+            file=sys.stderr,
+        )
+
+
 # =============================================================================
 # Sub-agent platform detection + JSONL context files
 # =============================================================================
@@ -1332,7 +1366,13 @@ def cmd_archive(args: argparse.Namespace) -> int:
             # missing from the active set are treated as completed.
             task_children = data.get("children", [])
 
-            # If this is a parent, clear parent field in all children
+            # If this is a parent, clear parent field in all children.
+            # Remember each link removed so a later failure in this loop can
+            # put it back (see _restore_child_links). Keyed by the child's
+            # task.json: a `children` list that names the same child twice
+            # would otherwise record a second, already-cleared snapshot and
+            # the restore would write that `null` back over the real parent.
+            unlinked_children: dict[Path, str | None] = {}
             if task_children:
                 for child_name in task_children:
                     child_dir_path = find_task_by_name(child_name, tasks_dir)
@@ -1351,13 +1391,29 @@ def cmd_archive(args: argparse.Namespace) -> int:
                                     file=sys.stderr,
                                 )
                                 continue
+                            # Only the first visit to a child records its original
+                            # parent: a `children` list naming the same child twice
+                            # would otherwise snapshot the already-cleared value and
+                            # the restore would write that `null` back over the link.
+                            first_visit = child_json not in unlinked_children
+                            original_parent = child_data.get("parent")
+                            if first_visit:
+                                unlinked_children[child_json] = original_parent
                             child_data["parent"] = None
                             if not write_json(child_json, child_data):
                                 # Stop before the move: a child pointing at a
                                 # parent that has left .trellis/tasks/ is a
                                 # dangling reference nothing repairs later.
+                                # Put back the children already unlinked above —
+                                # their parent is staying, so losing the link the
+                                # other way round is just as unrecoverable.
                                 # Retrying is safe — every step so far is
                                 # idempotent.
+                                if first_visit:
+                                    # The link never came off, so there is nothing
+                                    # to put back for this child.
+                                    del unlinked_children[child_json]
+                                _restore_child_links(unlinked_children)
                                 _report_write_failure(child_json)
                                 print(
                                     f"Not archived: {_repo_relative_path(task_dir, repo_root)} is "