RxJS 7 to RxJS Next migration

Treat this as reviewed project work, not a codemod run. The objective is an intentional RxJS Next contract backed by the project's own build and behavior evidence. A transformed file, a clean diff, or one passing test is not proof that the migration is complete.

Work through all eight stages in order. Re-enter an earlier stage whenever new evidence changes scope, coverage, or lifecycle intent. Keep the developer involved at every explicit pause.

Non-negotiable rules

• Read and obey repository-local instructions before acting. Protect existing work and stay within the authorized repository and paths.
• Establish the RxJS 7 baseline before changing dependencies or source.
• Never infer platform sharing versus producer-per-direct-subscription behavior from syntax, filenames, operator names, or a currently passing output.
• Use the installed engine's versioned registry and schemas as authority. Do not reconstruct capability mappings from this Skill or from memory.
• Run the deterministic engine without writes first. A refusal is a successful safety outcome, not permission to improvise a mechanical rewrite.
• Preserve the project's test fra…