[alexeybe1kin]

Hunt findings memorygate-2 F2 and F3.

• A skill body was accepted up to 12000 characters but cut to 8192 bytes on every read, so an editor that loaded and saved it stored the cut text. Now create and edit refuse a skill whose title and body exceed 8192 bytes (422), and reads return the stored text.
• In /context/skills, a skill that did not fit the remaining budget ended the loop (break), dropping every smaller skill after it. It is now skipped (continue).

Tests: two new tests in tests/test_skills.py, both failing on main. ruff and types ok.