fix CSCL LDF

[damonmcc]

related to #2522
all builds on this branch

• LDF header release IDs and dates come from recipe.yml. All four were unset, so int__ldf_header raised at compile time. Output now matches prod's published 26b header exactly: 26A / 02092026 / 26B / 04222026.
• The build loads its own LDF inputs. Previous-release LION, the previous LDF header, and prod's LDF were only ever loaded by hand into the shared production_outputs schema, so nothing kept them there.
• Citywide prod LION can be loaded again. load has aborted on a deliberate assert False since July: the citywide union reads bronx_lion, but the tables are named bronx_lion_dat. Nine QA models source the table it builds.
• The LDF is excluded from output file validation. Positions 91-100 carry a cumulative record number that diverges from prod's (CSCL-LDF-03), so a whole-line diff flags every record after the first divergence. qa__ldf_summary already compares positions 1-90. Both validation paths read the exclusion from recipe.yml, so they can't disagree about what gets compared.
• A missing S3 object reports s3://bucket/key instead of ClientError: 404 HeadObject. object_exists no longer reports a 403 as "not found". Eight tests added.

notes

production_outputs is a single shared schema in db-cscl, and the build now rewrites three of its tables with DROP TABLE ... CASCADE. Two concurrent CSCL builds will race. Giving each build its own copy means splitting the source group, which is more than this change warrants.

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.63%. Comparing base (03cb07f) to head (114f400).

Files with missing lines	Patch %	Lines
dcpy/utils/s3.py	92.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
dcpy/utils/s3.py	82.27% <92.00%> (+1.82%)	⬆️

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