Build templates/spawn-ui-rename.md — force substrate-grep before patch on UI rename tasks

Carry-forward from 2026-06-12 lesson, structurally enforced tonight per LEARNINGS 2026-06-13. PR #12182 needed 3 sub-agent spawns in 50 minutes to ship one rename because the first-pass spawn prompt only said 'rename Pending → Scheduled on Event Details' instead of 'first grep all *.tsx in apps/dashboard/packs/programs for the literal enum value, then patch every callsite'. Deliverable: templates/spawn-ui-rename.md with literal block including: 1. Substrate-grep step (grep -rln '"<enum_value>"' apps/dashboard/packs/<area>/) BEFORE patching 2. Enumerate all callsites in the spawn prompt body before naming the rename target 3. Promote any inline label rendering to a shared helper (events/_lib/getEventStatusLabel.ts pattern) 4. Defensive forward-compat for adjacent enum values 5. Tests covering each callsite for each enum value Same structural pattern as templates/spawn-commit-trailer.md (June 10 ship for the trailer rule). Cat the Literal block section verbatim into spawn prompts that involve UI label renames. First enforcement: next UI rename task that comes through carry-forward.