[FEATURE] Allow manually overriding session status + a 'Closed'/'Archived' state in agent view

Problem

In the agent view / background session list, each session is automatically assigned a status (Working, Needs input, Completed, etc.) that is inferred from the agent's output. There is currently no way to manually override this status.

This causes a practical problem: a session frequently gets auto-marked Completed when, from my perspective, the work is not actually done (the agent declared completion prematurely, or it satisfied its own heuristic but not my real acceptance criteria). Because I can't trust the auto-assigned Completed status, I lose the ability to use the status as a reliable filter — I have to re-open and re-read many sessions to figure out which ones genuinely need my attention.

The inverse also happens: a session I consider effectively finished/irrelevant stays in the list with no way to dismiss it, so the list accumulates noise.

Request

Add the ability to manually manage session status, ideally including:

1. Manual status override — let me move a session between states regardless of what the classifier inferred (e.g. force a wrongly-Completed session back to an "in progress / needs attention" state, or mark a still-Working one as done).
2. A Closed / Archived / Dismissed state — a way to hide or collapse sessions I want to ignore, without permanently deleting them. Today the only option is deletion (Ctrl+X twice / claude rm <id>), which is too destructive for "I just want this out of my active view."
3. (Nice to have) A CLI equivalent, e.g. claude status <id> <state> or claude archive <id>, plus a filter to show/hide archived sessions in the agent view.

Why this matters

The whole value of the status column is as a triage signal. When Completed can't be trusted and there's no Archived/manual-override escape hatch, the list stops being a reliable triage tool and I'm forced to manually inspect sessions one by one — which defeats the purpose of having statuses at all.

Current workarounds (and why they fall short)

• Delete the session (Ctrl+X twice / claude rm) — too destructive; loses the session from the active list and I may want it back.
• claude respawn <id> to pull a wrongly-Completed session back to Working — works, but it actually re-runs the agent rather than just correcting the status, which is overkill when I only want to fix a label.
• Rename (Ctrl+R) with a manual [done]/[ignore] prefix — purely cosmetic; statuses and filters don't respect it.

Environment

• Claude Code CLI, agent view / background sessions