/session picker should show session summary (name, recency, intent) inline

### Describe the feature or problem you'd like to solve

No low-friction way to see the current session's name and basic details (/session output is not helpful, /session info is more than I need). Terminal title sometimes shows stale value.

### Proposed solution

Show the same summary line in the /session picker that /resume shows: session name, locality, last-modified time, and the most recent intent.

Current:

> ❯ ● Session 1 (active)

Proposed:

> ❯ ● Session 1 (active): Local, modified 27m ago, created 1d ago - Review CLI PR

Alternatively, could be formatted as a table similar to the /resume picker.

This gives users an instant sanity check without leaving their flow, and makes the /session picker actually useful instead of being a near-empty box.

### Example prompts or workflows

1. Quick name check -- Run /session, confirm the name and intent match your current task, press Esc, keep working. Today this requires /session info and scanning through unrelated details.
2. Multi-stream context switching -- When juggling 3+ sessions across repos, naming discipline matters. Unless you choose a good name upfront, identifying the right session in /resume is hard. /session would now let you catch a bad name early before it becomes a problem.
3. Catching a stale title -- You renamed a session but the terminal title didn't update. /session gives you a trustworthy second source without the overhead of /session info.

### Additional context

The information already exists (it's rendered in /resume); this is mostly about surfacing it in one more place. Keeping the two pickers consistent would also reduce the cognitive gap when switching between them.