[arrzdev]

What

packages/abalone-engine holds every rule of the game but had no coverage report and no floor. This adds a test:coverage script (v8), tests for the branches the report showed as uncovered, and thresholds at today's numbers rounded down.

The CI gate already runs test:coverage instead of test for any package that defines it (.github/actions/gate/action.yml), so the workflow itself needs no change.

Coverage

	Before	After	Floor
Lines	99.29% (422/425)	99.29% (422/425)	99
Branches	94.75% (253/267)	98.12% (262/267)	98
Statements	98.69% (529/536)	99.25% (532/536)	99
Functions	100%	100%	100

moves.ts and rules.ts now reach 100% on every metric. New tests cover:

• destinationsFor: a line read toward a lower row gives the same squares in the same order as the same line read the other way.
• selectMarble: a white lead marble grows a white line and starts over on black.
• selectRun: a walk that runs off the board before it reaches its target gives up.
• goToMove: hand-edited history entries (no marbles, a destination that touches none, no shovedMarbles) still restore, just without the highlight.
• isValidSelection and undoTargetIndex: a bot game with no recorded colour behaves as if the human plays black.

None of the new tests found a rules bug.

What's still uncovered:

• game-state.ts:260: unreachable, since directionBetween already returned non-null for the anchor in the line above. Removing it would be a refactor, which is out of scope here.
• board-setups.ts and position.ts: setup-table helpers, not rules. They're left for a follow-up.

Verify

pnpm --filter @repo/abalone-engine test:coverage
pnpm typecheck && pnpm biome:check && pnpm exec turbo run build --filter=@repo/game...

[arrzdev]

Approve. Test-only change: the engine suite runs under coverage in the gate (CI log: 106 passed, branches 98.12%, all files over the floors), and the coverage-v8 version matches the one apps/game already uses. The two remaining gaps listed in the description are fine as follow-ups.