Add persistent save/resume for in-progress puzzle sessions

[Mkalbani]

Description

Currently a puzzle session is lost if the player quits mid-session (whether via TUI or future WASM/web frontend). Add a persistence layer so a session can be serialized to disk (native) or localStorage (WASM) and resumed later with the same puzzle state, elapsed time, hint count, and score-in-progress.

Acceptance Criteria

• Session struct derives Serialize/Deserialize (serde)
• save_session(path: &Path) and load_session(path: &Path) added to the persistence module
• Autosave triggers on answer submission and on hint reveal
• --resume <session_id> CLI flag loads the last saved session
• Corrupted or version-mismatched save files fail gracefully with a clear error, not a panic
• Unit tests cover save/load round-trip for at least 3 puzzle types

[OluRemiFour]

I've reviewed the task and have a clear implementation plan. Looking forward to contributing with a quality PR.

[Menjay7]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. I’ll prioritize this immediately and ensure a reliable solution is delivered as soon as possible. Thank you!

[jaynomyaro]

Hi! I’m a full-stack developer with a strong blockchain background, and I’m confident I can resolve this issue quickly and effectively. I’ll deliver a clean, reliable solution with immediate attention to detail, ensuring it’s completed as soon as possible. Please assign it to me—I’m ready to get started right away.

[VerifiedFlemzy1]

Hello boss, Please assign this issue to me. I checked it out and I am confident I will solve it
my eta is 2 hours

[Favouratambi]

Hi! I'd like to work on this issue.

My approach would be to implement a cross-platform persistence layer that allows puzzle sessions to be saved and resumed seamlessly across both native and WASM environments. I'll make the Session struct serializable with serde and add save_session/load_session APIs that abstract away the underlying storage mechanism (filesystem for native and localStorage for WASM).

I'll implement autosave after answer submissions and hint reveals to minimize progress loss, and add support for the --resume <session_id> CLI flag to restore the latest saved session. I'll also ensure corrupted or incompatible save files are handled gracefully with clear error messages rather than panics.

Finally, I'll add comprehensive unit tests covering save/load round-trips for multiple puzzle types, ensuring the restored session preserves puzzle state, elapsed time, hint count, and score accurately while keeping the implementation modular and maintainable.

[grantfox-oss]

🦊 GrantFox — @OluRemiFour has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #26)
2. Your PR will be reviewed by the ThinknetCollective maintainers

Good luck! Track your progress on GrantFox.