ADR-1 agent-lifecycle: non-blocking review follow-ups (wontfix-or-fold)

[brettchien]

Non-blocking items surfaced during the 8-axis review of ADR-1 (docs/adr/agent-lifecycle.md). All three reviewers gave FINAL LGTM; these are left to the author's discretion (wontfix or fold into a later revision).

• Stopping hard-loss edge — tighten the wording where a hard loss during Stopping goes straight to Stopped (vs the graceful Stopping→Stopped edge).
• §9 lock-in / reversibility — expand the lock-in note (which parts are expensive to reverse).
• R2 State.Paused — naming/enum consideration for the RuntimeDriver-contract ADR (ADR-2).
• superseded sentence — optional airtight tightening of the instance-level phrasing.

Raised by: Jellyfish, Mira, Falcon. Tracking here rather than blocking the merge.