Add --continue-on-error flag for map-data CLI

[amc-corey-cox]

Summary

• Adds TransformationError dataclass exception with structured context (class_derivation_name, slot_derivation_name, source_row, row_index)
• Single try/except in map_object's slot derivation loop converts exceptions to TransformationError with full context
• transform_spec() gains an on_error callback parameter: None = fail-fast (default), callback = collect and continue
• --continue-on-error CLI flag collects all row-level errors, reports summary to stderr, exits 1

Closes #162

Test plan

• Engine-level: bad rows collected via on_error callback, good rows yielded, fail-fast preserved when no callback
• CLI-level: --continue-on-error reports to stderr with exit 1; no errors = exit 0; without flag = fail-fast
• Existing tests pass (526 total, including updated exception expectations)
• just test full suite green

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds structured, row-level error handling to the transformation engine and exposes it via a new --continue-on-error flag in the map-data CLI, enabling “collect and continue” behavior while preserving default fail-fast semantics.

Changes:

• Introduces TransformationError carrying structured context (class/slot/row/row_index) for transformation failures.
• Adds an on_error callback to transform_spec() to collect row errors and continue processing.
• Extends map-data CLI with --continue-on-error to report a summary of errors and exit with code 1 when any occur.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/linkml_map/transformer/errors.py	Adds TransformationError dataclass with structured context + formatting.
src/linkml_map/transformer/object_transformer.py	Wraps slot-derivation exceptions as TransformationError with context.
src/linkml_map/transformer/engine.py	Adds on_error callback to collect/enrich row-level errors and continue.
src/linkml_map/cli/cli.py	Adds --continue-on-error flag; collects errors, prints summary, exits 1 if any.
tests/test_transformer/test_object_transformer.py	Updates exception expectation to TransformationError.
tests/test_transformer/test_continue_on_error.py	Adds engine/error-type unit tests for continue-on-error behavior.
tests/test_compliance/test_compliance_suite.py	Allows compliance tests to accept TransformationError wrapping.
tests/test_cli/test_cli_tabular.py	Adds CLI-level tests covering fail-fast vs continue-on-error behavior.

[madanucd]

LGTM! All 25 tests pass including the 3 new CLI tests and 8 new error handling tests. Fail-fast default is preserved and --continue-on-error is a clean opt-in for batch jobs where one bad row shouldn't kill the entire run. All Copilot feedback addressed.