feat(classifier): add rule for interface parent/extends removal (R32)

[Aakif-Kohari]

Summary

InterfaceSignature.extends?: string[] is extracted by all four language translators but is never consumed by any classification rule:

• src/parsers/translators/typescript.ts → extractExtends() (TS extends_type_clause / heritage_clause)
• src/parsers/translators/java.ts → extractExtendsInterfaces() (extends_interfaces)
• src/parsers/translators/go.ts → extractEmbeddedInterfaces() (embedded interfaces)
• src/parsers/translators/rust.ts → trait bounds

src/core/types.ts even flags this directly on the field:

// removing a parent interface = breaking — callers relying on inherited properties break

Right now if a contributor removes interface Foo extends Base → interface Foo,
Diff Guardian reports nothing, even though any caller relying on Base's members/type-compatibility through Foo silently loses that guarantee.

Proposed solution

Add R32: Interface Parent Removed — a new InterfaceRule that diffs oldSig.extends against newSig.extends and flags each parent present in the old signature but missing from the new one as breaking. Adding a new parent, or reordering existing ones, is not flagged (order-independent, addition-safe).

Since the field is already populated on all four translators, this is a classifier-only change — no parser/grammar work needed.

Scope

• src/classifier/rules/R32_interface_extends_removed.ts (new rule)
• src/classifier/rules/index.ts (export)
• src/core/types.ts (add interface_extends_changed to ChangeType)
• client/src/content/docs/rules-data.ts (docs entry)
• tests/rules/interface-rules.test.ts (unit tests: positive, safe-addition,
  safe-reorder, identical, empty-array edge case)

Alternatives considered

Reusing interface_property_removed as the changeType — rejected, since the PR report/reporter should be able to distinguish "a field disappeared" from "a parent contract disappeared"; they have different remediation paths for the consumer.

Assignment

I'd like to work on this issue under ECSoC26. Will open a PR only after approval/assignment by @Aryan0628 or another maintainer.
And after R31 (#32 ) is merged, to avoid conflicting with it on the shared docs/index files.

[Aryan0628]

Okay continue with the implementation.