fix(cfg): preserve labeled statement break targets

[MikeeI]

Summary

Register CFG break sinks for every valid labeled statement.
Keep labeled continue behavior restricted to iteration statements.

Evidence

• Current label registration exists only in loop lowering.
• A labeled block break consequently has no edge to its continuation.

Changes

• Scope a general label break sink around each inner statement.
• Keep labeled continue targets restricted to iteration statements.

Risks and boundaries

• Existing unlabeled and loop continue behavior remains unchanged.
• Parser and node-identity contracts remain out of scope.

Verification

• bun test test/dataflow.test.ts
• bun test
• bun run typecheck

I checked the relevant issues, comments, pull requests, and discussions; this pull request is not a duplicate.

Disclosure

Investigated thoroughly with GPT-5.6 at extra-high reasoning effort.
I used Oh My Pi as the agent framework.
This report is not generic or unreviewed AI-generated output.
Its claims were checked against the cited evidence.
It includes the relevant detail intended to help maintainers resolve the issue.
If reports like this are not useful to the project, please let me know.
I will refrain from submitting similar reports.
My intent is to help without wasting maintainer time or energy or discouraging their work.
Thank you for your work.