feat(realism): EditAction read-modify-write of planted files

Stage 3b of the realism migration. A TODO.md planted on Monday gets a
checkbox flipped on Tuesday; a notes file grows a follow-up line; a
cron log gets a fresh entry tacked on. The synthetic_files row's
edit_count, last_modified, and content_hash advance.

New surface:

- EditAction dataclass (peer of FileAction in scheduler.py): carries
  decky, path, persona, content_class, previous_body, mtime, and
  synthetic_file_uuid for the worker's update path.
- realism.bodies.next_iteration(cls, persona, prev, rng): per-class
  deterministic mutators. TODO flips an unchecked box and/or appends;
  notes/drafts/scripts append; logs are append-only (mirroring real
  log behaviour). Canary, cache_tmp, email raise KeyError —
  unsupported.
- realism.planner.pick gains an edit branch: 60% create, 30% edit
  (when an edit_candidate is supplied), 10% leave-alone. Returns
  None on leave-alone — quiet ticks are realism too.
- scheduler.pick_file pre-fetches a single edit candidate via
  repo.pick_random_synthetic_file_for_edit ~50% of ticks; the
  planner decides whether to use it.
- SSHDriver._run_edit: turns next_iteration output into a
  plant_file call (mtime-bumped, mode 0o644). Stashes new_body in
  result.payload so the worker can hash it for synthetic_files.
- worker._bump_synthetic_file_after_edit: patches edit_count + 1,
  last_modified=now, content_hash, last_body for the row UUID.
  No-op when the row was pruned mid-flight.
- events.to_row / topic_for / event_type_for now recognise
  EditAction (kind="file", action="file:edit").

decnet/orchestrator/events.py

@@ -6,7 +6,12 @@ from typing import Any
 
 from decnet.bus import topics as _topics
 from decnet.orchestrator.drivers.base import ActivityResult
-from decnet.orchestrator.scheduler import Action, FileAction, TrafficAction
+from decnet.orchestrator.scheduler import (
+    Action,
+    EditAction,
+    FileAction,
+    TrafficAction,
+)
 
 
 def to_row(action: Action, result: ActivityResult) -> dict[str, Any]:
@@ -31,6 +36,16 @@ def to_row(action: Action, result: ActivityResult) -> dict[str, Any]:
             src_decky_uuid=None,
             dst_decky_uuid=action.dst_uuid,
         )
+    elif isinstance(action, EditAction):
+        # EditAction shares the "file" kind (same dashboard view, same
+        # bus topic family) but action="file:edit" lets queries
+        # discriminate when needed.
+        base.update(
+            kind="file",
+            action=action.description,
+            src_decky_uuid=None,
+            dst_decky_uuid=action.dst_uuid,
+        )
     else:
         raise TypeError(f"unsupported action type: {type(action)!r}")
     return base
@@ -40,7 +55,7 @@ def topic_for(action: Action) -> str:
     """Map an action to its bus topic."""
     if isinstance(action, TrafficAction):
         return _topics.orchestrator(_topics.ORCHESTRATOR_TRAFFIC, action.dst_uuid)
-    if isinstance(action, FileAction):
+    if isinstance(action, (FileAction, EditAction)):
         return _topics.orchestrator(_topics.ORCHESTRATOR_FILE, action.dst_uuid)
     raise TypeError(f"unsupported action type: {type(action)!r}")
 
@@ -48,6 +63,6 @@ def topic_for(action: Action) -> str:
 def event_type_for(action: Action) -> str:
     if isinstance(action, TrafficAction):
         return _topics.ORCHESTRATOR_TRAFFIC
-    if isinstance(action, FileAction):
+    if isinstance(action, (FileAction, EditAction)):
         return _topics.ORCHESTRATOR_FILE
     raise TypeError(f"unsupported action type: {type(action)!r}")