Run history: list and inspect previous runs, not just the latest

[that-github-user]

Problem

thinktank list only shows results from the most recent run. All previous runs are stored as .thinktank/run-<timestamp>.json files but there is no way to:

• List all past runs
• Re-apply a result from a previous run
• Compare results across runs
• Clean up old run files

As runs accumulate, .thinktank/ grows indefinitely with no management tools.

Proposed Solution

thinktank list --all

List all past runs in reverse chronological order:

Past runs (7 total, 23 MB):

  #  Date                  Agents  Best  Tests  Convergence
  ─────────────────────────────────────────────────────────
  1  2026-03-28 14:23:01       5     3   4/5    Strong consensus
  2  2026-03-28 11:05:44       3     1   3/3    Moderate agreement
  3  2026-03-27 09:12:33       5     2   2/5    Divergent approach
  ...

Use: thinktank list --run 2    to inspect a specific run
     thinktank apply --run 2   to apply from a previous run

thinktank list --run <N>

Show full agent results for run N (same as current thinktank list but for any run).

thinktank apply --run <N> --agent <M>

Apply agent M's diff from run N (not just the latest run).

thinktank clean

Interactively clean up old run files:

$ thinktank clean
Found 12 run files (45 MB). Keep last N runs? [5]: 
Deleted 7 run files (32 MB freed).

Or non-interactively: thinktank clean --keep 5

Acceptance Criteria

• thinktank list --all lists all runs in .thinktank/ in reverse chronological order
• thinktank list --run <N> shows detailed results for a specific run by its position in the list
• thinktank apply --run <N> [--agent <M>] applies from a historical run
• thinktank clean [--keep N] deletes old run files, keeping the N most recent (default: 10)
• All commands handle empty history gracefully
• Run index is computed from file timestamps (no separate index file needed)

[that-github-user]

Fixed in #111. thinktank list shows all past runs in a table. thinktank list N shows details for run #N. Generated by thinktank Opus.