refactor: seal resilience manager structs pub(crate)

[pratyush618]

What

The resilience manager structs are public but serve only the in-crate Scheduler. No binding or sibling crate consumes them (bindings drive resilience through Storage methods directly). Seal them:

• CircuitBreaker (struct + methods) → pub(crate)
• RateLimiter (struct + methods) → pub(crate)
• DeadLetterQueue (struct + methods) → pub(crate)
• Delete Scheduler::circuit_breaker() — dead accessor, zero callers
• Delete DLQ list/retry/purge — no in-crate caller (would trip dead_code once sealed)

Kept public (config contract, already root-exported): RetryPolicy, RateLimitConfig, CircuitBreakerConfig, CircuitState.

Verify

All green:

• cargo test --workspace
• cargo check --workspace --features postgres,redis
• cargo clippy --workspace --all-targets -- -D warnings
• cargo doc --no-deps -p taskito-core with RUSTDOCFLAGS=-D warnings
• cargo publish --dry-run -p taskito-core

Summary by CodeRabbit

• Refactor
  • Resilience components are now internal implementation details rather than publicly accessible APIs.
  • Removed direct access to the scheduler’s circuit breaker.
  • Dead-letter queue listing, retry, and purge operations are no longer exposed externally.
  • Existing circuit breaker, rate limiting, and resilience behavior remains unchanged.

[coderabbitai]

📝 Walkthrough

Walkthrough

The change narrows resilience APIs to crate-only visibility, removes unused dead-letter queue management methods, and deletes the scheduler’s public circuit-breaker accessor. Internal circuit-breaker, DLQ, and rate-limiter behavior remains unchanged.

Changes

Resilience API Encapsulation

Layer / File(s)	Summary
Internalize resilience managers crates/taskito-core/src/resilience/*	CircuitBreaker, DeadLetterQueue, and RateLimiter types and methods now use pub(crate) visibility. DLQ list, retry, and purge methods were removed.
Remove scheduler breaker accessor crates/taskito-core/src/scheduler/mod.rs	The public Scheduler::circuit_breaker() accessor was deleted.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• ByteVeda/taskito#456: Touches the same resilience types and may relate to their API visibility adjustments.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: sealing resilience manager structs to crate-only visibility.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/core-seal-resilience-managers

---

_{Comment @coderabbitai help to get the list of available commands.}