fix: open --no-agent sets agent to 'shell' instead of inheriting session agent

[Wirasm]

Summary

When kild open --no-agent is used on a kild originally created with an agent (e.g., claude), the spawn record's agent field showed the session's original agent name instead of "shell". This caused incorrect display in kild list, kild status, and JSON output, though the actual command (/bin/zsh) ran correctly.

Root Cause

The BareShell match arm in open_session used session.agent.clone() (the session's original agent) instead of the literal "shell" that create_session correctly uses.

Changes

File	Change
crates/kild-core/src/sessions/handler.rs	Fixed BareShell arm to use "shell".to_string() matching create_session pattern

Testing

• cargo fmt --check passes
• cargo clippy --all -- -D warnings passes
• cargo test --all passes (all 874 tests)

Validation

cargo fmt --check && cargo clippy --all -- -D warnings && cargo test --all

Issue

Fixes #288

[Wirasm]

Automated Code Review

Summary

Clean, minimal fix that correctly addresses the root cause. No issues found.

Findings

Strengths

• Matches the established create_session pattern at line 75 exactly
• Removes the misleading comment alongside the fix
• Single-line change with zero blast radius — only affects spawn record metadata

Security

• No security concerns. Change is limited to a string literal in a metadata field.

Checklist

• Fix addresses root cause (BareShell arm using session's original agent instead of "shell")
• Code follows codebase patterns (mirrors create_session at line 75)
• All 874 tests pass
• No bugs introduced