Job Monitor: extract typed work-stream identity and lineage model

[mmitche]

Parent: #17171

Extract behavior-preserving, pure domain logic for identifying and ordering Helix work across attempts and resubmissions.

Scope

• Introduce explicit types for stage attempt, logical work-stream identity, and job incarnation.
• Move chain-key construction, lineage traversal, latest-incarnation selection, and old-to-new ordering out of mutable monitor state.
• Preserve queue-sensitive identity and higher-stage-attempt precedence.
• Add table-driven tests for malformed, incomplete, linked, and unlinked lineage.

Acceptance criteria

• Identity and lineage decisions require no service calls or mutable global state.
• Existing attempt-scoped and multi-attempt scenarios retain their behavior.
• MonitorState no longer owns lineage algorithms.

[mmitche]

Implementation is starting from current main now that #17178 and #17179 are merged. This remains a behavior-preserving extraction; existing attempt-scoped and multi-attempt scenarios are the regression boundary.

[mmitche]

Draft implementation is available in #17223.