[Feature Request] Extend the "Show this every time" confirm opt-out to task archiving

[adamatan]

Follow-up to #77 / #88, which added a "Don't ask again" opt-out to the tab-close confirm (now confirmBeforeCloseAgentTab) plus the Resume dropdowns that make closing/archiving non-destructive.

Archiving a task still only has a hard confirm every time, with copy that reads more alarming than it needs to given the task stays recoverable from the project's "+" menu and History. Two changes:

• Same opt-out pattern for archive. A "Show this every time" checkbox on the archive confirm (renamed from "Don't ask again" for clearer framing that unchecking it, not checking it, is the one-time action), backed by a new confirmBeforeArchiveTask setting (on by default), mirroring confirmBeforeCloseAgentTab. When off, archiving is instant with a toast pointing back at Resume.
• Softer confirm copy for both archive and tab-close, since the dialog can now say "easy to get it back" instead of implying the action is destructive.

Also folds in a small related fix in TerminalPane: a freshly minted session id was being persisted before the agent actually wrote its session file to disk, so a quick close+reopen could fail to resume ("No conversation found"). Now it's only persisted after the first real submit.

Mostly implemented locally already; opening this to track it before sending the PR.