fix(usage): count cached re-runs of runtime-linked prompt text (#347)

A PromptManager-family node whose text comes from a runtime link
(PreviewAny, an LLM, a list node) counted only the job that executed it;
later jobs served from ComfyUI's output cache counted nothing.

Each execution now records a receipt (digests of its STRING outputs and
hashes of the text it stores) per run key and queue item. On
execution_cached the receipt whose digests equal the cache entry's text is
replayed once for the job, with the node's role and what the queue hook
already saw recomputed from the job's own graph. The executing node and the
replay count through one shared own_counts. Unmatched cache entries count
nothing, as before; a node that executes after its replay in the same job
skips its own count. No schema change, no backfill.

utils/usage_tracking.py

@@ -16,7 +16,9 @@ it never counts. Servers without a ``prompt_queue`` fall back to counting at
 submit time.
 
 Text from known pure string nodes is resolved at queue time too. Anything else
-(PromptSearchList batches, unknown nodes) is counted by the node as it executes.
+(PromptSearchList batches, unknown nodes) is counted by the node as it executes,
+and when ComfyUI serves such a node from its cache, the job replays what that
+execution counted (``cached_runs``, #347).
 """
 
 import threading
@@ -167,13 +169,22 @@ def queued_pair_runs(graph: Any) -> List[Tuple[str, str, str]]:
 
 def find_pair_id(db: Any, positive: str, negative: str) -> Optional[int]:
     """Find a saved pair without creating or overwriting its metadata."""
-    positive_row = db.get_prompt_by_hash(generate_prompt_hash(positive))
-    negative_row = (
-        db.get_prompt_by_hash(generate_prompt_hash(negative))
-        if negative.strip()
-        else None
+    return find_pair_id_by_hashes(
+        db,
+        generate_prompt_hash(positive),
+        generate_prompt_hash(negative) if negative.strip() else None,
     )
-    if not positive_row or (negative.strip() and not negative_row):
+
+
+def find_pair_id_by_hashes(
+    db: Any, positive_hash: str, negative_hash: Optional[str]
+) -> Optional[int]:
+    """The saved pair of two prompt hashes; ``None`` negative is the empty one."""
+    positive_row = db.get_prompt_by_hash(positive_hash)
+    negative_row = (
+        db.get_prompt_by_hash(negative_hash) if negative_hash is not None else None
+    )
+    if not positive_row or (negative_hash is not None and not negative_row):
         return None
     row = (
         db.model.get_connection()