Add per-PR property tests and nightly fuzz job infrastructure:
CI Changes (declarative-config):
- pdftract-ci.yaml: Add proptest step to test-matrix
- New test-proptest template with configurable case count
- Sets PROPTEST_SEED for reproducibility
- Runs 10,000 cases per module within 1 CPU-hour budget
- pdftract-nightly-fuzz.yaml: Sync fuzz workflow
- CronWorkflow runs daily at 0400 UTC
- 5 fuzz targets with address sanitizer
- Seed corpus from malformed fixtures
Existing Infrastructure (Already in Place):
- Proptest suites for lexer, object_parser, xref, stream, cmap_parser
- Fuzz targets for all 5 modules
- proptest-regressions/ with README
- Seed corpus in fuzz/corpus/
Verification:
- Added tests/proptest-panic-verification.rs
- Proptest infrastructure correctly structured
- Will catch deliberate panics within budget
Closes: pdftract-33v
