Publish a horizon for Samples keyword aliases

## What to build

Give the deprecated Samples camelCase keyword aliases one published removal horizon through the package's shared deprecation mechanism. The aliases were introduced on 2026-08-07; use 2027-08-07, matching the repository's one-year horizon convention.

Both Samples getters must read that date from the central removal table and continue accepting and translating every legacy keyword exactly as they do now. This ticket schedules the aliases; it does not remove them or change their wire spellings.

## Acceptance criteria

- [ ] The central removal table contains one Samples-scoped horizon of 2027-08-07.
- [ ] Both Samples legacy-keyword shims emit advisories that name the usable replacement and print that horizon.
- [ ] No Samples deprecation still says only "in a future release."
- [ ] Tests obtain the expected horizon from the central table rather than duplicating the date literal.
- [ ] Every camelCase alias remains accepted and produces the same request as its snake_case replacement.
- [ ] Public signatures, parameter mappings, and Samples wire names are unchanged.
- [ ] The full offline suite and coverage gate pass.

## Blocked by

None — can start immediately.

Start by locating the shared central removal table and both Samples legacy-keyword getters, then inspect their existing deprecation tests and request-mapping behavior. Add the single 2027-08-07 horizon and verify advisories, unchanged alias translations, the full offline suite, and the coverage gate.

索引モデルが issue の本文から書いたものです。