feat(delegation): live-viewable subagent transcripts — tail your subagents while they work (#67479)

* feat(delegation): live-viewable subagent transcripts for delegate_task

Each child now streams an append-only, human-readable log to
<hermes_home>/cache/delegation/live/<delegation_id>/task-<n>.log while it
runs, and the dispatch return includes the paths so the caller can tail
them immediately instead of waiting blind for the consolidated summary.

- New tools/delegation_live_log.py: LiveTranscriptWriter (per-event append
  + flush, one-line rendering with truncation, never raises into the agent
  loop), wrap_progress_callback (tees the child's existing
  tool_progress_callback events into the log, preserves the _flush
  contract), dispatch-time creation with pre-headered files so tail -f
  attaches immediately, manifest.json (goals/task count/per-task status),
  and 7-day retention pruning on new dispatches.
- delegate_task: wraps each child's progress callback with the writer;
  sync results and background dispatch responses gain live_transcripts
  (+ hint field on dispatch); per-task result entries carry
  live_transcript; transcripts finalized with exit-reason markers.
- async_delegation: dispatch_async_delegation_batch accepts an optional
  delegation_id so the live/ dir name matches the returned handle; the
  completion event carries live_transcripts.
- process_registry: consolidated batch-completion block references each
  task's live transcript path.
- Tool schema description documents the live_transcripts return surface;
  docs gain a 'Live Transcripts' section with a tail -f example.

Placement under cache/delegation means the logs are mounted read-only
into remote terminal backends for free. Side-channel only: zero changes
to message content, so prompt caching is unaffected. Transcript-OUT only
— no overlap with the subagent control surfaces of PR #66046.

* fix(delegation): label the kickoff transcript line as user — it is the child's one user message

tools/process_registry.py

@@ -2119,6 +2119,11 @@ def _format_async_delegation(evt: dict) -> str:
                     + (f": {r_error}" if r_error else "")
                     + ")"
                 )
+            r_live = r.get("live_transcript")
+            if r_live:
+                lines.append(
+                    f"Full live transcript (complete tool/assistant trace): {r_live}"
+                )
         return "\n".join(lines)
 
     age = ""