fix: freeze elapsed timer for completed entries + 3s retention (v0.2.3)

[psh4607]

Summary

• Bug: "Done" entries displayed an ever-climbing elapsed time, looking like they were still running (e.g. `librarian Done 84m 2s` → `84m 3s` → `84m 4s` …).
• Fix: `completeEntry` now stamps `completedAt` only on the first terminal transition.
• Tweak: `COMPLETION_RETENTION_MS` 10s → 3s so completed rows fade faster.
• Bumped to v0.2.3.

Root cause

`completeEntry` unconditionally wrote `entry.completedAt = completedAt` on every call. That was fine in isolation, but the surrounding code re-invokes it once per second:

1. `tickTimer` calls `setNow(current)` every 1s while any agent is live.
2. The reactive `insert` callback re-runs (it depends on `now()` and `version()`) and calls `scanSessionState(sessionID)`.
3. `scanSessionState` walks every message part again. The `[ALL BACKGROUND TASKS COMPLETE …]` system reminder text is permanent in the message history, so its regex matches on every scan.
4. `completeEntry` is invoked again with `completedAt = Date.now()`, overwriting the original timestamp.

`renderAgentLine` computes `entry.completedAt - entry.startedAt`, so as `completedAt` advanced 1s per tick, the displayed elapsed time advanced 1s per tick. The entry was "Done" (gray) but visually behaved like it was still running.

It also caused unnecessary `bumpVersion` calls (since `completedAt` mismatch was reported as mutated), inflating render churn.

Change

```ts
const completeEntry = (entry: AgentEntry, status: AgentStatus, completedAt: number): boolean => {
const nextStatus = status === "error" ? "error" : "completed";
const statusChanged = entry.status !== nextStatus;
// Stamp completedAt only on the first transition to a terminal state.
// Re-stamping (e.g. when scanSessionState re-matches the same
// [ALL BACKGROUND TASKS COMPLETE] system reminder on every 1s tick) would
// make the elapsed timer keep climbing past completion, so a "Done" entry
// visually behaves like it's still running.
const stampChanged = entry.completedAt === undefined;
if (stampChanged) entry.completedAt = completedAt;
if (statusChanged) entry.status = nextStatus;
return statusChanged || stampChanged;
};
```

Status can still flip (e.g. `completed` → `error`) but the original completion timestamp is preserved.

Verification

• `bun run typecheck` ✅
• `bun run build` ✅ (dist/ regenerated)
• LSP diagnostics clean on `src/tui.ts`
• Manual: needs install + TUI restart to confirm visually; the call paths impacted are `upsertMainMessage`, `upsertToolPart`, and `handleBackgroundStatusText`. The first two only re-invoke `completeEntry` when their respective time fields change (idempotent), so this fix is targeted at the `handleBackgroundStatusText` re-match path that causes the visible bug.

Files changed

• `src/tui.ts` — fix + retention constant + version bump
• `package.json` — version 0.2.2 → 0.2.3
• `dist/tui.js`, `dist/tui.js.map`, `dist/tui.d.ts.map` — regenerated build output (committed per repo convention so `github:` installs are zero-config)

[Copilot]

Pull request overview

Fixes a UI bug in the TUI sidebar where completed (“Done”) agent entries kept showing an increasing elapsed time due to repeated rescans re-stamping completedAt, and shortens the post-completion retention window.

Changes:

• Make completeEntry stamp completedAt only on the first transition into a terminal state, preventing elapsed time from continuing to climb after completion.
• Reduce completed-entry retention from 10s to 3s so completed rows disappear sooner.
• Bump plugin/package version to 0.2.3 and regenerate distribution artifacts.

Reviewed changes

Copilot reviewed 2 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tui.ts	Freezes completedAt on first terminal transition; reduces completion retention; bumps plugin version constant.
package.json	Bumps package version to 0.2.3.
dist/tui.js	Regenerated build output reflecting the completeEntry and constants changes.
dist/tui.js.map	Updated sourcemap from regenerated build.
dist/tui.d.ts.map	Updated type-definition sourcemap from regenerated build.

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