v0.5.0 — Encounter Danger Board + Pair Detail

• UI split: the Token Controls skull button now opens an Encounter Danger Board as the main window. The single-PC vs single-enemy detail view lives in a separate Pair Detail popup (one reusable instance).
• Read PC and hostile NPC tokens from the active combat encounter without requiring individual token selection.
• Compute pairwise immediate down-risk for every supported (PC × hostile × Strike) triple by reusing the existing immediateDownRisk() engine.
• Danger board shows "Most endangered PCs" and "Most dangerous enemies" formatted as PC vs Enemy Attack — XX% Label. Each row has a Detail button that opens the Pair Detail window for that exact pair.
• A top-level "Open detail for selected PC + targeted enemy" button preserves the v0.4.x select-and-target workflow.
• Catch per-pair errors so one bad Strike does not poison the whole encounter board.
• Add a MAX_PAIRS = 200 performance guardrail that short-circuits to a skipped board with a clear caveat instead of freezing Foundry on very large scenes.
• Graceful errors if a referenced token is no longer on the canvas (combat ended or scene changed).
• Remove the previous combined MortalityPanel and its template.
• Update docs/ARITHMETIC.md, docs/TESTING.md, and BACKLOG.md to match the split UX.

Grim Arithmetic v0.4.2

Alpha compatibility metadata release. Marks Grim Arithmetic as verified against Foundry VTT v14.361 after initial server smoke testing; no runtime code changes were required.