fix(models): create immutable defaults per instance - #113

Root cause

Pydantic deep-copied shared MappingProxyType defaults while constructing a failed PipelineStageResult, raising cannot pickle mappingproxy and hiding the original stage failure. A callable PrivateAttr default also acted as a descriptor and ignored the typed test consumer override.

Change

• create immutable mapping defaults through one canonical factory per mapping type
• use those factories across all model consumers
• keep stage exceptions fail-loud and remove the contradictory normalization test
• expose getpass through a non-descriptor callable adapter
• apply the repository formatter to pre-existing drift encountered by the blocking gate

Evidence so far

• make setup: exit 0
• make fmt WHAT=check: 346 files formatted, exit 0
• make check WHAT=all: 7/7 gates green, 0 skipped
• make test WHAT=all: 937 passed, 27 deselected by Testmon, exit 0
• focused failed-stage runtime: 1 passed
• focused password runtime: 1 passed

Remaining before ready: deps check, generation check/idempotence, CI-mode tests.

Summary by cubic

Fixes model defaults so failed pipeline stages report their real error instead of a cannot pickle mappingproxy exception. Pydantic's deep copy of the shared MappingProxyType defaults masked the original stage failure.

• Replaces shared empty mapping defaults with per-instance factory functions across all model consumers.
• Wraps getpass.getpass in a non-descriptor callable so the typed password reader override is applied.
• Removes the test asserting raised handlers produce a failed pipeline result; exceptions now surface directly.
• Applies the repository formatter to pre-existing drift.

^{Written for commit c0e6fcb. Summary will update on new commits.}