Merge origin/tier2/module_taxonomy_refactor_20260627: bring in v2 SHIPPED work

Per post_module_taxonomy_de_cruft_20260627 Phase 0 prerequisite.
Master is at 6344b49f (pre-merge of v2 SHIPPED). This merge brings in
the 18 v2 SHIPPED commits that define the destination modules
(src.mma, src/project.py, src/project_files.py, src.tool_presets,
src.tool_bias, src.external_editor, src.personas,
src.workspace_manager, src.mcp_client) needed by the Phase 2
consumer migration in commit 8f11340b.

Conflicts resolved (all were import-block re-orderings between my
migration's update and v2 SHIPPED's update of the same files):
 - src/external_editor.py: took v2 SHIPPED version (class definitions
                                    + the no-alias import pattern)
 - src/personas.py: took v2 SHIPPED version
 - src/tool_bias.py: took v2 SHIPPED version
 - src/tool_presets.py: took v2 SHIPPED version
 - src/workspace_manager.py: took v2 SHIPPED version
 - src/ai_client.py: took v2 SHIPPED version (removes the 'as _FIC'
                              alias; uses 'from src.project_files import
                              FileItem' directly per the v2 SHIPPED style)
 - conductor/tracks/module_taxonomy_refactor_20260627/spec.md: took
                              HEAD version (my Phase 1 VC2 + VC10
                              corrections; the v2 SHIPPED version was
                              the pre-correction spec)

src/external_editor.py

@@ -6,10 +6,64 @@ import subprocess
 import tempfile
 
 # TODO(Ed): Eliminate these?
-from pathlib import Path
-from typing  import Optional, List, Dict, Any
+from dataclasses import dataclass, field
+from pathlib     import Path
+from typing      import Optional, List, Dict, Any
 
-from src.result_types import ErrorInfo, ErrorKind, Result
+from src.result_types    import ErrorInfo, ErrorKind, Result
+from src.type_aliases    import Metadata
+
+
+@dataclass
+class TextEditorConfig:
+ name:      str = ""
+ path:      str = ""
+ diff_args: List[str] = field(default_factory=list)
+
+ def to_dict(self) -> Metadata:
+  return {
+   "name":      self.name,
+   "path":      self.path,
+   "diff_args": self.diff_args,
+  }
+
+ @classmethod
+ def from_dict(cls, data: Metadata) -> "TextEditorConfig":
+  return cls(
+   name      = data["name"],
+   path      = data["path"],
+   diff_args = data.get("diff_args", []),
+  )
+
+
+@dataclass
+class ExternalEditorConfig:
+ editors:        Dict[str, TextEditorConfig] = field(default_factory=dict)
+ default_editor: Optional[str] = None
+
+ def get_default(self) -> TextEditorConfig:
+  if self.default_editor and self.default_editor in self.editors:
+   return self.editors[self.default_editor]
+  if self.editors:
+   return next(iter(self.editors.values()))
+  return EMPTY_TEXT_EDITOR_CONFIG
+
+ def to_dict(self) -> Metadata:
+  return {
+   "editors":        {k: v.to_dict() for k, v in self.editors.items()},
+   "default_editor": self.default_editor,
+  }
+
+ @classmethod
+ def from_dict(cls, data: Metadata) -> "ExternalEditorConfig":
+  editors = {}
+  for name, ed_data in data.get("editors", {}).items():
+   if   isinstance(ed_data, dict): editors[name] = TextEditorConfig.from_dict(ed_data)
+   elif isinstance(ed_data, str):  editors[name] = TextEditorConfig(name=name, path=ed_data)
+  return cls(editors=editors, default_editor=data.get("default_editor"))
+
+
+EMPTY_TEXT_EDITOR_CONFIG: TextEditorConfig = TextEditorConfig()
 
 
 class ExternalEditorLauncher:
@@ -47,7 +101,7 @@ class ExternalEditorLauncher:
   except FileNotFoundError as e:
    return Result(data=None, errors=[ErrorInfo(kind=ErrorKind.NOT_FOUND, message=f"Editor binary not found: {cmd[0]}", source="external_editor.launch_diff_result", original=e)])
 
- 
+
 
 
 _cached_vscode_config: Optional[TextEditorConfig] = None