feat(protogen): infer feature imports from ProtoFileOptions and sort options deterministically

[Kybxd]

Summary

When generating .proto files via bookExporter.export, language-specific
feature options (e.g. features.(pb.go).*, features.(pb.cpp).*,
features.(pb.java).*) used to require callers to also manually declare the
matching *_features.proto imports, and the emitted option lines came out
in Go's non-deterministic map iteration order.

This MR fixes both issues.

Changes

internal/protogen/exporter.go

• Infer feature imports from ProtoFileOptions. While building the import
  set, scan each option key and add the corresponding well-known proto:
  • features.(pb.go) → google/protobuf/go_features.proto
  • features.(pb.cpp) → google/protobuf/cpp_features.proto
  • features.(pb.java) → google/protobuf/java_features.proto
    Because imports are kept in a treeset keyed by path, duplicates are
    naturally deduplicated and output stays sorted by import path.
• Emit option lines in alphabetical order of the key instead of relying
  on Go's randomized map iteration, producing stable, diff-friendly output.

internal/protogen/exporter_test.go

• New table-driven Test_bookExporter_export covering:
  • proto3 baseline output.
  • edition = "2023" with features.utf8_validation.
  • edition = "2024" with features.strip_enum_prefix.
  • Import inference for each of pb.go / pb.cpp / pb.java in isolation,
    asserting that only the matching *_features.proto is imported.
  • All three language features together, asserting that all three imports are
    added and options appear in the file.
  • Alphabetical ordering of option keys when they are defined in a
    non-alphabetical order in the input map.
• Tests use real options defined in protobuf's go_features.proto /
  cpp_features.proto / java_features.proto (api_level, string_type,
  utf8_validation, legacy_closed_enum, ...) rather than synthetic names.

.github/workflows/*.yml (lint / testing / release / publish-module-to-bsr)

• Formatting-only changes produced automatically by the VSCode "GitHub
  Actions" extension on save (e.g. [master, main] → [ master, main ],
  minor spacing normalizations). No workflow semantics are changed.

Compatibility

• Public API of bookExporter is unchanged.
• For users that already imported *_features.proto manually, the import set
  deduplicates via treeset, so no duplicate import lines are produced.
• Option output order changes from random to alphabetical, which may affect
  byte-for-byte comparisons of previously generated files but not their
  semantics.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.38%. Comparing base (e7a79d9) to head (aa6ff1b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #400      +/-   ##
==========================================
+ Coverage   73.35%   73.38%   +0.03%     
==========================================
  Files          88       88              
  Lines       11284    11300      +16     
==========================================
+ Hits         8277     8293      +16     
  Misses       2440     2440              
  Partials      567      567              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.