Fix #197: auto-expand fineGrainedHashExternalRepos through bzlmod wrappers

[tinder-maxwellelliott]

Summary

• Fixes #197 — specifically the wrapper shape @Ahajha called out in his comment: a target inside one external repo is re-wrapped by another external repo, and the main repo consumes only the wrapping repo. Before this fix, changing the inner repo's source file did not invalidate the main consumer unless every wrapping repo was manually enumerated in --fineGrainedHashExternalRepos.
• The fix walks bazel mod graph --output=json once at startup, builds the apparent-name dep graph, and auto-adds every bzlmod module that transitively depends on a user-listed repo to the fine-grained set. Listing only @inner_repo is now enough; @middle_repo is added automatically so its alias rule is queried for real and its actual attribute carries the dep chain down to the leaf source file.
• The expansion is a no-op when the user supplies no repos, when bzlmod is disabled, or when no wrapper depends on a listed repo, so existing flows that don't involve wrapping repos behave exactly as before.
• The reproducer test added in the previous revision of this PR is now a non-@Ignore'd regression test under the new wrapped_external_repo fixture.

Mechanism

• New entry point: expandFineGrainedHashExternalReposWithBzlmodDependents in cli/src/main/kotlin/com/bazel_diff/di/Modules.kt.
• New parser helpers on ModuleGraphParser (parseModuleGraphEdges, findTransitiveDependents) extract the dep edges from the JSON form of bazel mod graph and run reverse-BFS from the user-listed apparent names, excluding the root module (which is always queried via //...:all-targets anyway).

Manual verification

With the fixture from this PR:

• --fineGrainedHashExternalRepos=@inner_repo after editing inner_repo/data.txt:
  • Before: impacted = {@inner_repo//:all_files, @inner_repo//:data.txt} — //:consumer is not impacted (bug).
  • After: impacted = {//:consumer, //:consumer.out, @inner_repo//:all_files, @inner_repo//:data.txt, @middle_repo//:wrapped} — //:consumer is impacted (fixed).
• --fineGrainedHashExternalRepos=@inner_repo,@middle_repo still works (the manual-enumeration workaround is unaffected).

Test plan

• bazel test //cli:ModuleGraphParserTest — passes (5 new tests for the edge + dependents helpers).
• bazel test //cli:E2ETest --test_filter=".*WrappedExternalRepo.*" — the regression test for No impacted targets when a file in an external repository changes #197 now passes without @Ignore.
• Full E2E suite locally on Bazel 9.1.0: same 4 pre-existing failures as the PR base (testFineGrainedHashExternalRepo, testBzlmodTransitiveDepsCquery, testUseCqueryWithExternalDependencyChange, testUseCqueryWithAndroidCodeChange — all fail on the unmodified base too due to a Found duplicate artifact versions com.google.guava:guava issue in the existing maven fixture zips; CI runs on Linux and passes them).
• Manual run with the locally built CLI confirms the fix (see "Manual verification" above).

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