Check that group skills select and dispatch what they should #66

Category: feature
Area: Evaluation (tests/scenarios)
Impact: The group skills decide which items get worked and what each item is told. A wrong selection or a dropped input is invisible to the item-level scenarios.
Confidence: traced

Problem (the use case)

scripts/scenario.mjs skips group skills. Their contracts promise things worth testing: at most *_batch items, oldest first, each one passing the item skill's requires, stuck and human-merge items excluded, drafts excluded for review, and every dispatch given write_log=false plus the inputs the item also lists. The dispatch-forwarding fix in #51 has no test beyond the contract text.

Proposed solution

Add scenarios for the five group skills under tests/scenarios/<group>/, with a dispatches: expectation listing the items, in order, and the inputs each was given.

• Selection: a world with more eligible items than the batch, an ineligible one, and a stuck one. Assert the batch and the order.
• Forwarding: assert write_log=false and every shared input the item lists (runner, unattended, trusted_authors, ...), and none that it does not.
• Log: one entry whose results match the dispatched items.
• The checker uses the real item contract's params to decide what must be forwarded.

Acceptance criteria

• The checker supports dispatches: for group skills.
• At least three scenarios for each of the five group skills, including nothing eligible.
• A scenario that drops trusted_authors from a dispatch fails.
• triage-github-issues is covered, including its call to reconcile-github-issues.

Non-goals

Running the dispatched items.

Size: medium