feat: add wrap_with_*_context and deserialize_to_snapshot APIs (v0.8.1)

[Yaming-Hub]

Summary

Adds two new API categories that close gaps in the context inheritance model:

1. Wrap helpers — capture context without spawning

Function	Source	Description
wrap_with_sync_context(mode, fut)	sync (thread-local)	Returns a future with task-local context
wrap_with_async_context(mode, fut)	async (task-local)	Returns a future with task-local context

These decouple context capture from task spawning. The existing spawn_with_* helpers always call tokio::spawn immediately, but many patterns need to capture context now and spawn later:

• Task queues / backpressure — enqueue a context-carrying future on a bounded channel
• Retry wrappers — capture context once, create wrapped futures for each retry
• Rate limiters — capture at request time, execute when a slot opens
• Priority queues — wrap, assign priority, spawn highest-priority first

Both support Fork (cheap Arc sharing) and Snapshot (full copy) modes.

2. deserialize_to_snapshot — wire bytes → ContextSnapshot directly

pub fn deserialize_to_snapshot(bytes: &[u8]) -> Result<ContextSnapshot, ContextError>

Converts wire bytes directly into a ContextSnapshot without mutating any live context store. Previously, the only way was a three-step dance:

// Before: deserialize into live store, snapshot, then drop
let _guard = sync_ctx::deserialize_context(&bytes)?;
let snap = sync_ctx::snapshot();
drop(_guard);

// After: direct conversion, no side effects
let snap = dcontext::deserialize_to_snapshot(&bytes)?;

Benefits:

• No thread-local/task-local mutation
• Single pass (no double work)
• Works on any thread (no task-local store required)

Changes

• dcontext/src/inheritance.rs — added wrap_with_sync_context, wrap_with_async_context
• dcontext/src/wire.rs — added deserialize_to_snapshot
• dcontext/src/lib.rs — re-exports for new APIs
• dcontext/src/tests.rs — 9 new tests (5 wrap, 4 deserialize)
• dcontext/Cargo.toml — version bump 0.8.0 → 0.8.1

Test Results

All 88 tests pass, zero clippy warnings.