Refactor concurrency policy traits handlers

[FrozenLemonTee]

No description provided.

[Copilot]

Pull request overview

Refactors the concurrency policy layer by replacing the prior atomic policy with a set of fenced* policies that inject configurable memory-order fences, and adds an explicit handler protocol for primitive load/store/CAS operations via concurrency policies.

Changes:

• Replace policy::concurrency::atomic with policy::concurrency::{fenced, fenced_relaxed, fenced_acq_rel, fenced_seq_cst} and extend concurrency injection to carry std::memory_order.
• Add concurrency “access handler” protocol/concepts and implement primitive load/store/compare_exchange via std::atomic_ref-backed handlers.
• Update tests, examples, and README to reflect the new concurrency policy names and semantics.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/basic/test_policies.cpp	Updates policy trait/concurrency handler tests for fenced* policies and verifies injected memory orders + access-handler availability.
tests/basic/test_operations.cpp	Renames atomic-policy tests to fenced-policy tests and adds coverage for primitive load/store/CAS under fenced policy.
src/primitive/impl.cppm	Adds primitive concurrency policy resolution and new load/store/compare_exchange APIs using concurrency access handlers.
src/policy/utility.cppm	Updates concurrency policy priority ordering to prefer fenced over none.
src/policy/impl.cppm	Introduces fenced* policy tags/traits and implements inject() + std::atomic_ref access handlers for these policies.
src/policy/handler.cppm	Extends concurrency injection with memory orders and adds handler access protocol/availability concepts.
src/operations/invoker.cppm	Threads injected memory orders through runtime fences (atomic_thread_fence(order)).
README.md	Updates documented concurrency policies and adds documentation + example for primitive concurrency access APIs.
examples/ex07_custom_policy.cpp	Updates custom policy example to set injected fence memory orders.
examples/ex05_concurrency_policy.cpp	Updates concurrency example to use fenced policy and demonstrates primitive load/store/CAS.

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