decision-to-code-proximity: applies-to vocabulary — land the decision code-scope section

[tcballard]

Sub-issue of #273 (decision-to-code-proximity, ADR-093).

Corpus: rac/requirements/rac-decision-applies-to-scope.md — the existing gap-7 requirement, adopted as this roadmap's Initiative 1.

Scope:

• Optional ## Applies To section on decisions, recognised and extracted like other optional sections; additive (ADR-007), classification-neutral (adjacent-type tests hold).
• Path-style entries existence-checked by rac relationships --validate; component names recorded without resolution (labels, no registry semantics this cycle).
• Literal paths and directories are the validated form; glob entries are accepted as declared match patterns whose matching semantics belong to the lookup (Epic: decision-to-code-proximity — decisions at the point of edit #273's Initiative 2).
• Surfaced via get_related/MCP for scoped grounding.
• Evidence decisions (adr-018, adr-023, adr-027, adr-033) declare checkable scope as the dogfood proof.

Delivery also ticks the decision-scope (gap 7) box on #236. Tick on #273 when landed.