Bump bundled buildozer 7.1.2 → 8.5.1 for bazel mod tidy / buildifier parity

[alexeagle]

Summary

bazel mod tidy rewrites/reformats MODULE.bazel using the buildozer binary
pinned in src/MODULE.tools (@buildozer_binary, via BazelModTidyFunction).
This fork pins buildozer 7.1.2, which predates buildtools
PR #1345 "Keep include calls together in MODULE.bazel files"
(first shipped in buildozer v8.2.0). As a result, mod tidy inserts a blank
line between every consecutive include() call.

Standalone buildifier 8.5.1 (what consumers pin via buildifier_prebuilt, and
what pre-commit hooks run) does have bazelbuild#1345 and keeps include() calls compact.
So MODULE.bazel flip-flops depending on which tool touched it last — a formatter
version skew, not a logic bug in either tool.

This bumps the bundled buildozer to 8.5.1, matching buildifier and eliminating
the disagreement. It ports the intent of upstream
bazelbuild/bazel #28650
("Update buildozer to v8.5.1"), which landed on master (→ 9.x) but was never
backported to the 8.x LTS line — so 8.6/8.7 remained on 7.1.2.

Changes

• src/MODULE.tools: buildozer 7.1.2 → 8.5.1

⚠️ Required follow-up — lockfile regeneration (CI will be red until done)

buildozer 8.5.1 adds a dependency on rules_shell 0.3.0; this fork currently
resolves rules_shell 0.2.0, so this is a real module-resolution change, not a
hash swap — the lockfiles must be regenerated by Bazel (per the note at the top of
src/MODULE.tools):

bazel run //src/test/tools/bzlmod:update_default_lock_file
bazel mod deps --lockfile_mode=update

I could not run these from my environment (needs the fork's Bazel in a full
checkout). This matches how figma/figma#837553 handled MODULE.bazel.lock
regeneration as a build step.

Test plan

• Regenerate MODULE.bazel.lock and src/test/tools/bzlmod/MODULE.bazel.lock
• Fork CI green
• Cut a 8.7.0-figmaN release and verify bazel mod tidy leaves consecutive
  include() calls compact (no blank lines), matching buildifier 8.5.1

🤖 Generated with Claude Code

[alexeagle]

Superseded by figma/figma#842013. That PR fixes the same buildifier vs bazel mod tidy disagreement entirely in-repo by declaring buildozer 8.5.1 as a root bazel_dep (MVS raises the version @bazel_tools' @buildozer_binary resolves), so no Bazel fork change or 8.7.0-figmaN release is needed. Verified: bazel mod tidy keeps consecutive include() calls compact. Closing.