## Summary

Adds support for Bazel's `--incompatible_no_implicit_file_export` flag
to comply with the new visibility requirements for file exports.

## Changes

- ✅ Enabled `incompatible_no_implicit_file_export` flag in
`shared.bazelrc`
- ✅ Added explicit `exports_files()` declarations for all `.bzl` files
referenced across package boundaries:
  - `bazeldoc/BUILD.bazel` - exports `defs.bzl`
  - `bzlformat/BUILD.bazel` - exports `defs.bzl`
  - `bzllib/BUILD.bazel` - exports `defs.bzl`
  - `bzlrelease/BUILD.bazel` - exports `defs.bzl`
  - `bzltidy/BUILD.bazel` - exports `defs.bzl`
  - `ci/BUILD.bazel` - exports `defs.bzl`
  - `markdown/BUILD.bazel` - exports `defs.bzl`
  - `updatesrc/BUILD.bazel` - exports `defs.bzl`
  - `shlib/rules/BUILD.bazel` - exports `execute_binary.bzl`
- ✅ Upgraded `buildifier_prebuilt` from `7.3.1` to `8.2.1.1` for
compatibility
- ✅ Added explicit `rules_python` `1.8.0` dependency to override
transitive `1.0.0` (includes [PR
#3471](bazel-contrib/rules_python#3471) fix)

## Test Plan

- [x] All 362 tests pass with `bazel test //...`
- [x] Build succeeds with the incompatible flag enabled
- [x] No visibility errors from implicit file exports

## Related Issues

Fixes #566

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>