feat(cli): open picker for bare resume

[mohitranka]

Summary

• show the navigable session picker for bare --resume
• highlight the most recently modified session
• create a new session with a notice when no previous sessions exist
• cancel without creating a session; preserve explicit IDs and /resume behavior

Validation

• cargo fmt --all -- --check
• cargo test -p forge-cli
• cargo test -p forge-tui --lib (683 passed)
• `git diff --check

[mohitranka]

Fixed in ec091d7: the temporary session journal created while the startup picker is open is now removed after both cancellation and successful selection. This prevents empty journals from appearing in future resume lists.

Validation: cargo fmt --all -- --check, cargo test -p forge-cli, and cargo test -p forge-tui --lib (683 passed).

[mohitranka]

Fixed the CI failure in 3b95695: Clippy rejected identical if branches in the resume startup flow. The condition is now collapsed into one expression.

Validated locally with cargo fmt --all -- --check, cargo clippy --workspace --all-targets --locked -- -D warnings, and cargo test -p forge-cli.