Validate case metadata before use

[rogerchappel]

Summary

• add regression coverage for malformed top-level and entry metadata fields
• validate every persisted case and entry field before returning from loadCase
• make list/show/add/search/export fail with a concise field-specific diagnostic and prevent partial add writes
• document corrupt metadata repair behavior

Commits

• test: reject malformed case metadata shapes
• fix: validate case metadata before use
• docs: explain invalid metadata recovery

Verification

• npm ci --ignore-scripts --no-audit --no-fund
• pre-fix: npm run build && node --test dist/test/clipcase.test.js (new regressions failed as expected)
• npm run release:check (26 tests, typecheck, build, smoke, package smoke, release contract)
• bash scripts/validate.sh
• git diff --check origin/main...HEAD

All commit author and committer identities were verified as Roger Chappel miscanalysis@gmail.com.

[rogerchappel]

Automated merge note

Triage class: auto-merge

Summary: Validates persisted case/entry metadata, adds regression coverage, and documents recovery behavior.

Checks run: CI test (20), test (22), and test (24) — SUCCESS; diff and mergeability rechecked immediately before merge.

Rebased/CI-repaired: No.

Verified head SHA: 8f010dd1c31531b5be46bba760180ae79bc63e2c.