[adeeluddin01]

Summary

Fixes #864. The math_animate safety scan checked import roots against a
denylist, but did not account for standard-library modules that re-export a
blocked module as an attribute. import zipfile is not blocked, and
zipfile.os is the real os module, so a scene could reach host command
execution while the scan reported zero violations — on the default path,
without allow_unsafe_code.

What changed (tools/graphics/math_animate.py)

The scan (_scan_scene_code) gains three rules. All existing
denylist / blocked-name / dunder rules and their messages are unchanged.

1. Re-exported module attribute access is a violation. An attribute
   access whose name is itself a blocked module, rooted on a name bound by
   an import, is flagged — e.g. zipfile.os, tarfile.os, chained forms,
   aliased imports (import zipfile as z; z.os), and rebinding forms
   (x = zipfile; x.os). Taint from imports propagates through plain
   rebinding assignments so rebinding does not hide the module.
2. Importing a blocked name from any module is a violation — e.g.
   from zipfile import os.
3. Star-imports from modules other than manim are violations — e.g.
   from zipfile import * (which would otherwise bind unknown names,
   possibly a blocked module, without any import node naming them).
   from manim import * stays allowed: it is how scenes get Manim's API.

A small helper, _attr_root_name, resolves the root name of an attribute
chain for rule 1.

Tests (tests/tools/test_math_animate_safety.py)

7 new regression tests for #864:

• test_blocks_os_via_reexported_module (zipfile.os, top level)
• test_blocks_os_via_reexport_inside_construct (tarfile.os)
• test_blocks_aliased_reexport (import zipfile as z)
• test_blocks_reexport_via_rebinding (x = zipfile; x.os)
• test_blocks_from_import_of_blocked_name (from zipfile import os)
• test_blocks_star_import_from_non_manim (from zipfile import *)
• test_safe_scene_attribute_access_still_passes

Full suite run locally against the fixed module: 27 passed
(20 existing + 7 new). The existing safe scene (manim + numpy +
math, using np.pi / math.tau) still passes, so legitimate scenes are
unaffected — no breaking change.

Scope notes (honest)

• This closes the math_animate safety scan bypass: unblocked stdlib module re-exports os, allowing host command execution on the default path #864 re-export class. The static scan remains
  defense-in-depth, not a sandbox (as the file header states); a full
  sandbox for Manim execution is separate future work.
• The TeX-string and Code(code_file=...) file-read observations noted
  in math_animate safety scan bypass: unblocked stdlib module re-exports os, allowing host command execution on the default path #864 are not addressed here and remain open observations.
• The downstream Manim run was not executed live during this work (no
  Manim/LaTeX on the analysis machine); verification is at the scan level
  plus the repo's test suite.