assignment --force list still restores and reuses saved Blackboard session

[JKay15]

Summary

On current upstream head 58d4e0c63979fa6d7056e39df94a407e64bad14d, assignment --force list still restores ~/Library/Caches/org.sshwy.pku3b/ua.json and reuses that Blackboard session if it is valid. The command therefore ignores the fresh-session part of --force.

Reproduction

Environment used for the reproduced run:

• macOS
• current upstream binary built from 58d4e0c63979fa6d7056e39df94a407e64bad14d
• existing cfg.toml for a valid account
• temporary HOME containing only that config and a valid Blackboard cookie jar copied to the legacy shared path ~/Library/Caches/org.sshwy.pku3b/ua.json

Reproduction steps:

1. Create a fresh temporary HOME.
2. Symlink the existing cfg.toml into ~/Library/Application Support/org.sshwy.pku3b/cfg.toml under that temporary home.
3. Create ~/Library/Caches/org.sshwy.pku3b/ under that temporary home.
4. Copy a valid Blackboard session cookie jar into ~/Library/Caches/org.sshwy.pku3b/ua.json.
5. Run:

env HOME=/tmp/pku3b-upstream-force-reuse.XXXXXX NO_COLOR=1 RUST_LOG=info /private/tmp/pku3b-upstream-58d4e0c-node1/target/release/pku3b assignment --force list

Observed result

The command exits 0, prints the normal assignment listing, and logs:

• [INFO pku3b::api::builder] Cache TTL: None
• [INFO pku3b::api::builder] Download Artifact TTL: None
• [INFO pku3b::api::blackboard] reuse saved login session

That shows --force disabled the TTL caches but still restored and reused the saved Blackboard session.

Expected result

assignment --force list should not restore or reuse a saved Blackboard login session. It should start from a fresh Blackboard session path for that run.

Why this appears to be happening

The current upstream flow still wires the shared cookie-restore path in the force case:

• src/utils.rs:26-27 uses one shared Blackboard cookie path: projectdir().cache_dir().join("ua.json")
• src/cli/mod.rs:138-146 always sets cookie_restore_path(Some(utils::default_user_agent_data_path()))
• src/cli/mod.rs:150-154 calls build_client(!force), so force disables TTL caching but does not disable Blackboard cookie restore/save
• src/api/blackboard.rs:6-21 reuses any restored session whose Blackboard homepage preflight succeeds and logs reuse saved login session
• src/http.rs:48-65 saves and loads the cookie jar directly on that shared path

Distinction from nearby issues

This is different from the other open Blackboard session bugs:

• not the cache-path failure in #44, because the cache path is valid here
• not the cross-account reuse in #45, because the configured account is unchanged here
• not the stale-session reauthentication failure in #46, because the saved session is valid and the command succeeds by reusing it