Relay annot creation failures with err-dict resps

Change annot-ctl APIs to return `None` on failure instead of invalid
`aid`s. Server now sends `{'error': msg}` dict on failures, client
match-blocks handle gracefully.

Also,
- update return types: `.add_rect()`, `.add_arrow()`, `.add_text()`
  now return `int|None`
- match on `{'error': str(msg)}` in client IPC receive blocks
- send error dicts from server on timestamp lookup failures
- add failure handling in `markup_gaps()` to skip bad rects

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/tsp/_annotate.py

@@ -220,7 +220,16 @@ async def markup_gaps(
         )
 
         # add up/down rects
-        aid: int = await actl.add_rect(**rect_kwargs)
+        aid: int|None = await actl.add_rect(**rect_kwargs)
+        if aid is None:
+            log.error(
+                f'Failed to add rect for,\n'
+                f'{rect_kwargs!r}\n'
+                f'\n'
+                f'Skipping to next gap!\n'
+            )
+            continue
+
         assert aid
         aids[aid] = rect_kwargs
         direction: str = (

piker/ui/_remote_ctl.py

@@ -155,12 +155,14 @@ async def serve_rc_annots(
                         1: ds.chart,
                     }[timeframe]
                 except KeyError:
-                    log.warning(
+                    msg: str = (
                         f'No chart for timeframe={timeframe}s, '
                         f'skipping rect annotation'
                     )
-                    await annot_req_stream.send(-1)
+                    log.exeception(msg)
+                    await annot_req_stream.send({'error': msg})
                     continue
+
                 cv: ChartView = chart.cv
 
                 # NEW: if timestamps provided, lookup current indices
@@ -179,21 +181,23 @@ async def serve_rc_annots(
                     # lookup start index
                     start_matches = arr[arr['time'] == start_time]
                     if len(start_matches) == 0:
-                        log.error(
-                            f'No shm entry for start_time='
-                            f'{start_time}, skipping rect'
+                        msg: str = (
+                            f'No shm entry for start_time={start_time}, '
+                            f'skipping rect'
                         )
-                        await annot_req_stream.send(-1)
+                        log.error(msg)
+                        await annot_req_stream.send({'error': msg})
                         continue
 
                     # lookup end index
                     end_matches = arr[arr['time'] == end_time]
                     if len(end_matches) == 0:
-                        log.error(
+                        msg: str = (
                             f'No shm entry for end_time={end_time}, '
                             f'skipping rect'
                         )
-                        await annot_req_stream.send(-1)
+                        log.error(msg)
+                        await annot_req_stream.send({'error': msg})
                         continue
 
                     # get close price from start bar, open from end
@@ -587,7 +591,7 @@ class AnnotCtl(Struct):
         start_time: float|None = None,
         end_time: float|None = None,
 
-    ) -> int:
+    ) -> int|None:
         '''
         Add a `SelectRect` annotation to the target view, return
         the instances `id(obj)` from the remote UI actor.
@@ -610,7 +614,11 @@ class AnnotCtl(Struct):
                     'end_time': end_time,
                 },
             })
-            aid: int = await ipc.receive()
+            aid: int|dict = await ipc.receive()
+            match aid:
+                case {'error': str(msg)}:
+                    log.error(msg)
+                    return None
             self._ipcs[aid] = ipc
             if not from_acm:
                 self._annot_stack.push_async_callback(
@@ -692,7 +700,7 @@ class AnnotCtl(Struct):
         # NEW: optional timestamp for server-side index lookup
         time: float|None = None,
 
-    ) -> int:
+    ) -> int|None:
         '''
         Add a `SelectRect` annotation to the target view, return
         the instances `id(obj)` from the remote UI actor.
@@ -721,7 +729,12 @@ class AnnotCtl(Struct):
                     'time': time,  # for server-side index lookup
                 },
             })
-            aid: int = await ipc.receive()
+            aid: int|dict = await ipc.receive()
+            match aid:
+                case {'error': str(msg)}:
+                    log.error(msg)
+                    return None
+
             self._ipcs[aid] = ipc
             if not from_acm:
                 self._annot_stack.push_async_callback(
@@ -748,7 +761,7 @@ class AnnotCtl(Struct):
         # NEW: optional timestamp for server-side index lookup
         time: float|None = None,
 
-    ) -> int:
+    ) -> int|None:
         '''
         Add a `pg.TextItem` annotation to the target view.
 
@@ -772,7 +785,11 @@ class AnnotCtl(Struct):
                     'time': time,  # for server-side index lookup
                 },
             })
-            aid: int = await ipc.receive()
+            aid: int|dict = await ipc.receive()
+            match aid:
+                case {'error': str(msg)}:
+                    log.error(msg)
+                    return None
             self._ipcs[aid] = ipc
             if not from_acm:
                 self._annot_stack.push_async_callback(