What: Add format validation when reading ~/.10dev/developer-profile.md. Check YAML frontmatter required fields (developer, updated, version, pattern_count) and blind spot entry required fields (Keywords, Trigger, Frequency, Severity).
Why: The project's own lessons.md #8 states "Schema must be enforced, not just documented." Current malformed handling only catches YAML parse failures, not missing/invalid fields. Other tools or manual edits could produce a syntactically valid but semantically incomplete profile.
Pros: Prevents silent failures when profile is incomplete. Catches issues early with clear error messages.
Cons: Requires defining "valid" strictly. May break forward/backward compatibility if schema evolves. Agent-driven validation adds complexity to prompt instructions.
Context: Identified during eng review (2026-04-04). The profile format is defined in docs/state-files.md. Current malformed handling is in design doc section "Malformed profile handling" (check .bak, skip corrupt files). The gap is between "YAML parses" and "all required fields present."
Depends on: Stable profile format (current schema in state-files.md).