Add scheduler inspection and explicit control methods #18

Priority

p2 — Uncovered API parity; no concrete user demand has been verified.

Gap

These explicit operations have no matching SDK method after pending PR #2/#3/#5/#6 source composition. They are distinct from internal node protocols and alternate routes for already-covered workflows.

• GET /api/v1/schedulers/ — release and main
• POST /api/v1/schedulers/cq/reload — release and main
• POST /api/v1/schedulers/retention/trigger — release and main

Sources: internal/api/scheduler.go.

Acceptance

• Confirm intended SDK scope; document a reasoned exclusion for low-level operational APIs where appropriate.
• For included operations, add matching sync/async methods with exact request/response contracts and release/main version limits.
• Preserve role/license/configuration gates and server errors; test missing permissions and unsupported versions.
• Give mutating controls explicit arguments and safe defaults; test on isolated resources.
• Keep independently reviewable/rollbackable changes separate; do not turn this family issue into a mandatory single large PR.

Tracking: https://github.com/Basekick-Labs/ops/issues/40. Analysis baselines: SDK main 46d3b66 and pending PRs #2/#3/#5/#6; Arc release e83bb1e (v26.09.3) and main a63f4a8. Implementation is unscheduled; the parent analysis deadline is 2026-10-30. No owner or delivery commitment is implied.

Verification must record exact versions/commands/results and separate Manual Test from IA Test. Require sync/async cases, negative authorization/validation cases, and existing-regression preservation. Local Docker is appropriate for end-to-end server checks; inventory and clean up only test resources.