Collapse default skill/qual-level titles in the release data

[saturnflyer]

Summary

• Enlisted skill_levels and officer qual_levels repeated a :title for every ladder rung of every specialty, even though it's almost always a fixed function of the digit (enlisted 1/3/5/7/9 = Helper/Apprentice/Journeyman/Craftsman/Superintendent; officer 3/4 = Qualified/Staff). :code stays as extracted (it's the extractor's verified, verbatim-from-PDF ground truth).
• Only elide a level's title when one value covers the vast majority (>=90%): all enlisted levels qualify, but officer levels 1-2 reflect a real flying vs. non-flying doctrinal split with no dominant default, so those stay fully explicit.
• Enlisted already had a fallback for an omitted title, but its level-9 default was wrong ("Senior Enlisted Leader" instead of the actual majority, "Superintendent" — 84/88 real entries). Officer had no fallback at all and needed one added, or an elided title would have resolved to nil.
• The extractor (bin/extract_afsc_from_pdf.rb) now strips a rung's :title when it matches the runtime default, reusing the same SKILL_LEVELS/QUAL_LEVELS constants the lookup fallback uses (single source of truth, no duplicated map).
• Regenerated both 2025-10-31 release YAMLs from the source PDFs; the diff is title lines disappearing only where they match the new defaults — no :code/:name/:shredouts changes.