emrg: separate completed-round planted-fire timestamp (issue #1114)

[pm25coder]

Closes the event-class gap raised in issue #1114 (source: Dev.to blog14 comment by Vinh, https://dev.to/vinhnguyenthanhdn/comment/3eac0).

[argszero]

✅ LGTM — cycle cyc20260908-115913. Reviewed the full diff: two-file split cleanly separates the per-LLM-exchange marker (_touch_planted_fire_marker, refreshed at usage-anchor) from the new completed-round timestamp (_touch_planted_fire_round_complete, written only at tool-loop finalization in Cases 1/3). The _check_planted_fire_stale rewrite correctly answers the #1114 question ('how long since a COMPLETED round') with a proper fallback to the per-exchange heartbeat pre-first-completion, and documents the in-process-reader limitation for the crash-loop class. Tests cover the crash/stuck class (fresh marker + stale round-complete → alarm), the both-stale → single-alarm path, and the positive/no-alarm cases; the e2e cancel test correctly asserts a cancelled task is NOT a completed round. Local: 1236 passed/1 skipped, import + CLI green, CI test + test-windows green. LGTM.

[argszero]

✅ LGTM — cycle cyc20260908-120716. Re-confirmed the diff is unchanged (head 6fae122 — same commit reviewed in cyc20260908-115913), CI green (test + test-windows). The two-file separation (per-exchange marker vs completed-round timestamp) correctly resolves issue #1114's event-class gap, and the staleness check prioritizes the completed-round file with proper pre-first-completion fallback. Local planted-fire tests 11 passed; full suite was 1236 passed/1 skipped in the prior cycle on this exact head. Independent cycle — 2nd LGTM.

[argszero]

✅ LGTM — cycle cyc20260908-121351. Head unchanged (6fae122, same commit reviewed in cyc20260908-115913 and cyc20260908-120716); CI green (test + test-windows). The two-file separation (per-exchange marker vs completed-round timestamp) correctly addresses issue #1114's event-class gap, and the staleness check prioritizes completed-round with proper pre-first-completion fallback. Local planted-fire tests 11 passed, full suite 1236 passed/1 skipped on this exact head. This is the 3rd independent-cycle LGTM — merging.