refactor(aggregate_directives): expose importable aggregate_directives(preset_path, max_chars, project_root) function

Wraps the body-building core in a public aggregate_directives() function that
returns the rendered string and raises FileNotFoundError/ValueError on errors.
The existing aggregate() CLI wrapper catches those and preserves the prior
stdout/file output behavior. parse_preset now accepts an optional root param so
directive paths inside the preset resolve against a caller-supplied
project_root instead of always REPO_ROOT. No behavior change for the CLI; the
new function is the API surface used by the upcoming MCP server tool.

scripts/aggregate_directives.py

@@ -23,7 +23,9 @@ ENTRY_RE = re.compile(r"^\s*-\s+(?P<name>[A-Za-z0-9_]+)\s*:\s*(?P<path>\S+)\s*$"
 EXPECTED_PATTERN_TEMPLATE = r"^conductor/directives/{name}/v\d+\.md$"
 
 
-def parse_preset(preset_path: Path) -> list[tuple[str, Path]]:
+def parse_preset(preset_path: Path, root: Path | None = None) -> list[tuple[str, Path]]:
+ if root is None:
+  root = REPO_ROOT
  entries: list[tuple[str, Path]] = []
  for line in preset_path.read_text(encoding="utf-8").splitlines():
   m = ENTRY_RE.match(line)
@@ -31,36 +33,53 @@ def parse_preset(preset_path: Path) -> list[tuple[str, Path]]:
    continue
   name = m.group("name")
   rel_path = m.group("path")
-  abs_path = (REPO_ROOT / rel_path).resolve()
+  abs_path = (root / rel_path).resolve()
   entries.append((name, abs_path))
  return entries
 
 
-def aggregate(preset_path: Path, output_path: Path | None) -> int:
- entries = parse_preset(preset_path)
+def aggregate_directives(preset_path: str | Path, *, max_chars: int = 0, project_root: str | Path | None = None) -> str:
+ """
+ Read preset at preset_path, resolve each directive's v1.md, concatenate bodies.
+
+ Reads ONLY v1.md (never meta.md). Returns the concatenated string.
+ Raises FileNotFoundError if the preset or any referenced v1.md is missing,
+ ValueError if the preset is empty or any v1.md fails UTF-8 decoding.
+
+ preset_path   : path to the presets markdown file (absolute or relative to project_root)
+ max_chars     : if > 0, truncate the rendered body to this many chars and append a suffix note
+ project_root  : override for the project root (defaults to the module's REPO_ROOT)
+ """
+ root = Path(project_root).resolve() if project_root is not None else REPO_ROOT
+ p = Path(preset_path)
+ if not p.is_absolute():
+  p = (root / p).resolve()
+ if not p.exists():
+  raise FileNotFoundError("preset file not found: " + str(p))
+ entries = parse_preset(p, root=root)
  if not entries:
-  print("ERROR: no directive entries found in " + str(preset_path), file=sys.stderr)
-  return 1
+  raise ValueError("no directive entries found in " + str(p))
  missing: list[tuple[str, Path]] = []
  bodies: list[tuple[str, str]] = []
  for name, path in entries:
   if not path.exists():
    missing.append((name, path))
    continue
-  rel = path.relative_to(REPO_ROOT).as_posix()
+  try:
+   rel = path.relative_to(root).as_posix()
+  except ValueError:
+   rel = str(path)
   pattern = EXPECTED_PATTERN_TEMPLATE.format(name=re.escape(name))
   if not re.match(pattern, rel):
    print("WARNING: " + name + ": path " + str(path) + " does not match pattern conductor/directives/" + name + "/vN.md; including anyway", file=sys.stderr)
   try:
    body = path.read_text(encoding="utf-8")
   except UnicodeDecodeError as e:
-   print("ERROR: " + name + ": UTF-8 decode error in " + str(path) + ": " + str(e), file=sys.stderr)
-   continue
+   raise ValueError(name + ": UTF-8 decode error in " + str(path) + ": " + str(e)) from e
   bodies.append((name, body))
  if missing:
-  for name, path in missing:
-   print("ERROR: missing file for directive '" + name + "': " + str(path), file=sys.stderr)
-  return 1
+  names = ", ".join(n for n, _ in missing)
+  raise FileNotFoundError("missing v1.md files for directives: " + names)
  out_lines: list[str] = []
  for name, body in bodies:
   out_lines.append("=" * 40)
@@ -71,9 +90,22 @@ def aggregate(preset_path: Path, output_path: Path | None) -> int:
   out_lines.append("")
   out_lines.append("")
  rendered = chr(10).join(out_lines)
+ if max_chars > 0 and len(rendered) > max_chars:
+  truncated = rendered[:max_chars]
+  suffix = chr(10) + chr(10) + "[truncated: showing " + str(max_chars) + " of " + str(len(rendered)) + " chars; omit max_chars for full text]"
+  rendered = truncated + suffix
+ return rendered
+
+
+def aggregate(preset_path: Path, output_path: Path | None) -> int:
+ try:
+  rendered = aggregate_directives(preset_path)
+ except (FileNotFoundError, ValueError) as e:
+  print("ERROR: " + str(e), file=sys.stderr)
+  return 1
  if output_path:
   output_path.write_text(rendered, encoding="utf-8")
-  print("Wrote " + str(len(bodies)) + " directives to " + str(output_path), file=sys.stderr)
+  print("Wrote " + str(rendered.count("=" * 40) // 2) + " directives to " + str(output_path), file=sys.stderr)
  else:
   sys.stdout.write(rendered)
   if not rendered.endswith(chr(10)):