feat(ground): bind repeated-bounce request execution

[d-sorgcodexagent]

Refs #4270
Refs #4267

Depends on #4356 (2387430fc78baa92ba122c7ad008a498118bf62d).

Summary

• add one UI-neutral Python binding from the strict repeated-bounce request envelope to the existing solver
• consume the request-bound capture threshold and return the existing identity-validated request/result pair
• preserve preflight cancellation as a valid empty-ledger pair
• export the binding through the ground package and document the exact boundary

Verification

• 28 focused executor/public-contract tests pass independently
• complete ground suite: 189 passed
• manifest/layout: 11 passed
• Ruff check/format, Black, protected changed-file MyPy, Bandit, placeholder/diff, docs, quality, test-policy, and size gates pass

Deliberately still open

• UI request construction and invocation
• TypeScript or compiled physics
• request/result persistence and playback
• regional chaining, calibrated terrain, downstream parity, protected release, and Ground Model: validated 3D impact impulse and repeated bounce #4270/EPIC: Qualified Ball Landing, Bounce, Roll, and Ground-Surface Modeling #4267 completion

A broader import-following MyPy probe reports three inherited redundant casts in unchanged modules; the protected changed-file profile is green.

[dieterolson]

Consolidated into #4409. Closing to reduce CI/CD runner load.