file_read: remove max size limit, use islice for streaming reads

The 8MB size check caused models to fall back to cat which reads the
entire file without truncation. Now uses itertools.islice to read only
the requested segment without loading the whole file into memory.

Also: sandbox config additions (pcfs, ~/img).

sandbox/default.yaml

@@ -27,6 +27,7 @@ filesystem:
     - "{XDG_CONFIG_HOME}/gh"
     - "{XDG_DATA_HOME}/gh/extensions"
     - "/dev"
+    - "{HOME}/img"
   rw:
     - "{OLLIE_MEMORY_PATH}"
     - "{OLLIE_PLAN_PATH}"
@@ -75,6 +76,7 @@ filesystem:
     - "/dev/random"
     - "/dev/null"
     - "/dev/fuse"
+    - "{PCFS}"
   rox:
     - "/usr"
     - "/lib"
@@ -135,5 +137,6 @@ env:
   - EDITOR
   - GIT_SEQUENCE_EDITOR
   - SUPERPOWERD_SESSION_TOKEN
+  - PCFS
 network:
   unrestricted: true

tools/file_read

@@ -5,10 +5,10 @@
 
 import sys
 import os
+from itertools import islice
 
 MAX_LINES = 2000
 MAX_LINE_LEN = 2000
-MAX_SIZE = 8 * 1024 * 1024
 
 if len(sys.argv) < 2:
     print("usage: file_read <file_path> [start] [end]")
@@ -30,24 +30,21 @@ if not os.path.isfile(file_path):
     print(f"error: not a regular file: {file_path}")
     sys.exit(1)
 
-size = os.path.getsize(file_path)
-if size > MAX_SIZE:
-    print(f"error: file too large ({size} bytes, max {MAX_SIZE})")
-    sys.exit(1)
-
 with open(file_path, 'rb') as f:
     if b'\x00' in f.read(8192):
         print("(binary file)")
         sys.exit(0)
 
-with open(file_path, 'r', errors='replace') as f:
-    all_lines = f.readlines()
-
-total = len(all_lines)
 start = max(1, start)
-end = min(end, total) if end is not None else min(total, start + MAX_LINES - 1)
+if end is None:
+    end = start + MAX_LINES - 1
 
-segment_lines = all_lines[start - 1:end]
+with open(file_path, 'r', errors='replace') as f:
+    # Skip lines before start
+    for _ in islice(f, start - 1):
+        pass
+    # Read only the lines we need
+    segment_lines = list(islice(f, end - start + 1))
 
 if not segment_lines:
     print("(empty file)" if start == 1 else "(no lines in range)")