feat: add session reload command

[benvinegar]

Summary

• add hunk session reload (<session-id> | --repo <path>) -- <hunk command> so agents can swap the contents of a live Hunk TUI in place
• route a new reload action through the session daemon/websocket bridge and preserve the same session identity while refreshing registration metadata
• remount the app shell on reload so it behaves like restarting the session with new input, and cover the flow with CLI, daemon, help, and live session tests

Examples

hunk session reload --repo . -- diff
hunk session reload --repo . -- diff main...feature -- src/ui
hunk session reload --repo . -- show HEAD~1 -- README.md

Verification

• bun run format:check
• bun run lint
• bun run typecheck
• bun test
• bun run check:pack