task(cross-refs): add cross-reference sections to reckon and research skills

[pentaxis93]

Summary

reckon is the most-referenced skill in the system — eight protocols and skills
point to it — yet it has no cross-references section. An implementer reading
reckon has zero visibility into where it fires or what consumes its output.
research has the same gap: referenced by survey and orient, points back
to nothing.

Both skills need cross-reference sections that show where they integrate into
the protocol/skill topology.

Part of: #187

Scope

• skills/reckon/SKILL.md — add ## Cross-References section
• skills/research/SKILL.md — add ## Cross-References section

Acceptance criteria

• reckon/SKILL.md has a ## Cross-References section listing protocols and skills that invoke it, with one-line relationship descriptions
• research/SKILL.md has a ## Cross-References section listing protocols and skills that invoke it, with one-line relationship descriptions
• Each reference describes the relationship direction (what the referencing protocol/skill uses reckon or research for)
• References are accurate — derived from actual documented trigger points and artifact flows, not invented

Dependencies

None — these files have no existing cross-reference content to coordinate with.

[pentaxis93]

Closing: this issue was part of an epic (#187) that misframed the survey finding as a cross-reference formatting problem. The actual finding — reckon needs to be an explicit ceremony element in decompose — is addressed by #186. The cross-reference gaps identified here are real but incidental; they can be refiled accurately as maintenance work if pursued later.