feat: support event driven for sequences

[kerthcet]

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Special notes for your reviewer

Does this PR introduce a user-facing change?

[Copilot]

Pull request overview

This PR introduces an event-driven, FSM-based sequence lifecycle manager backed by a block allocator/manager, along with documentation and an example demonstrating basic usage. This appears to be foundational infrastructure for managing sequence scheduling, token append, forking, preemption, and completion in a structured way.

Changes:

• Added a block_manager subsystem (allocator + manager + types/errors) to allocate/refcount/free KV-cache-like blocks.
• Added a sequence_manager subsystem implementing an event-driven FSM with typed states and transition events, plus a thread-safe SequenceIdGenerator.
• Added developer-facing documentation (docs/fsm_architecture.md) and an executable example (examples/fsm_usage.rs), and introduced thiserror for error derivations.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
src/sequence_manager/states.rs	Defines FSM state types/variants and helper methods for sequence lifecycle tracking.
src/sequence_manager/mod.rs	Declares the sequence_manager module (and should expose a usable public API surface).
src/sequence_manager/id_generator.rs	Adds a thread-safe sequential SequenceId generator with unit tests.
src/sequence_manager/fsm_manager.rs	Implements the event loop and handlers for applying FSM transitions per sequence.
src/sequence_manager/fsm_events.rs	Defines the event/transition types that transform SequenceState with resource ownership semantics.
src/sequence_manager/events.rs	Defines the event protocol and stats payload used to drive/query the manager.
src/main.rs	Wires new modules into the binary crate.
src/lib.rs	Introduces a library surface re-exporting modules for external use (examples depend on this).
src/block_manager/types.rs	Adds block/sequence IDs, block stats, and thiserror-based error types.
src/block_manager/mod.rs	Declares the block_manager module (and should expose a usable public API surface).
src/block_manager/manager.rs	Implements block allocation, refcounting, free pooling, and stats reporting.
src/block_manager/allocator.rs	Defines the allocator trait and a simple CPU allocator implementation.
examples/fsm_usage.rs	Demonstrates end-to-end usage of the FSM sequence manager via async event sending.
docs/fsm_architecture.md	Documents the FSM approach, state diagram, and usage patterns for contributors.
Cargo.toml	Adds thiserror dependency.
Cargo.lock	Locks thiserror dependency version.

Comments suppressed due to low confidence (1)

src/block_manager/mod.rs:4

• This module is used from the example as puma::block_manager::{BlockManager, CpuAllocator}, but block_manager/mod.rs currently only declares submodules and doesn't re-export those types. As a result, the example (and any downstream crate using the same import style) will not compile.

pub mod allocator;
pub mod manager;
pub mod types;

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 16 changed files in this pull request and generated 11 comments.

[kerthcet]

/kind feature

[Copilot]

Pull request overview

Copilot reviewed 22 out of 23 changed files in this pull request and generated 6 comments.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 23 changed files in this pull request and generated 7 comments.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 23 changed files in this pull request and generated 6 comments.