nisse-review: read long files in parts; a retry starts afresh

From its failed review of #156: read_file stopped at 20,000 characters
with no way on, so the reviewer hunted each file's end a definition at a
time and ran out of turns; its retry carried every read before it, and a
model call timed out. Both drafts were lost.

- read_file takes a start line and says where the next part starts.
- Each run's view starts at its brief (Transcript.since); the log keeps
  the rest.
- A run out of turns with points drafted posts them as a partial review.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

nisse-review/src/nisse_review/reader.py

@@ -27,9 +27,11 @@ MAX_ISSUES = 20
 REF = "head (the PR's code) or base (the branch it merges into)."
 READ_FILE = tool(
     "read_file",
-    "Read a file in the repository. Its lines are numbered, for comment.",
+    "Read a file in the repository. Its lines are numbered, for comment. A "
+    "long file comes in parts: the end of each says where the next starts.",
     path="The file's path from the repository root.",
     ref=REF,
+    start="Optional: the line to start from (1, the default, is the top).",
 )
 LIST_FILES = tool(
     "list_files",
@@ -131,11 +133,27 @@ class Repository:
         lines = self.lines(path, ref)
         if lines is None:
             return ToolOutcome(f"{path}: no such file at {ref}", False)
-        text = "\n".join(f"{n:>5}  {line}" for n, line in enumerate(lines, 1))
-        if len(text) > MAX_FILE_CHARS:
-            more = len(text) - MAX_FILE_CHARS
-            text = text[:MAX_FILE_CHARS] + f"\n[{more} more characters not shown]"
-        return ToolOutcome(f"[{self.repo}@{ref}: {path}]\n{text}", True)
+        raw = str(arguments.get("start") or "1").strip()
+        if not raw.isdigit() or not 1 <= int(raw) <= max(len(lines), 1):
+            return ToolOutcome(f"start is a line number from 1 to {len(lines)}", False)
+        # A part of at most MAX_FILE_CHARS, in whole lines; the rest is a
+        # read away, never out of reach (#156: a long file's end was).
+        first = int(raw)
+        shown: list[str] = []
+        size = 0
+        for n in range(first, len(lines) + 1):
+            row = f"{n:>5}  {lines[n - 1]}"
+            if shown and size + len(row) + 1 > MAX_FILE_CHARS:
+                break
+            shown.append(row[:MAX_FILE_CHARS])
+            size += len(row) + 1
+        last = first + len(shown) - 1
+        where = f"lines {first}-{last} of {len(lines)}"
+        more = (
+            f"\n[{where}: read on with start={last + 1}]" if last < len(lines) else ""
+        )
+        text = "\n".join(shown)
+        return ToolOutcome(f"[{self.repo}@{ref}: {path}, {where}]\n{text}{more}", True)
 
     def _list(self, arguments: Mapping[str, Any]) -> ToolOutcome:
         folder = str(arguments.get("path", "")).strip().strip("/")