W replay wrapper: packaging changes

Changed pre-existing file: checks/replay_W_chain.py
All scientific checker files, archived mathematical result JSONs and selected
proof notes are unchanged. Their hashes are recorded in SOURCE_MAP.json.

Changes to the wrapper, with no change to its mathematical checks:
1. Replaced machine-specific source/output defaults with a script-relative
   proof_sources/W_research source and a caller-cwd-relative replay_new_W
   output. Explicit --source and --out arguments remain supported.
2. Replaced the tutorial example with a command runnable from the package root.
3. Replaced absolute source/output receipt strings with documented logical
   roots: source_root identifies the directory selected by --source; '.' is
   the directory containing the receipt. Source-file paths stay relative to
   source_root. Output, log and cwd paths stay relative to the receipt.
4. Recorded replay commands as ['python3', script_basename] with
   cwd='working_copy'. The actual execution still uses the current interpreter
   and its isolated working directory; the recorded Python version remains
   in the receipt. The absolute interpreter path is not persisted.
5. Added an explicit runner_variant description and path_convention metadata.
6. A missing selected-file assertion now names its relative source member.
7. The final stdout summary names replay_receipt.json without an absolute path.

No scientific equations, parameters, checker order, input caps, comparison
rules, or archived bytes were changed. No checksum equality check was weakened.
The nine field-cap bindings and twelve-monomial residual check are unchanged.
The original 31-file W input closure is preserved.

The actual child commands and raw scientific stdout are not rewritten by this
wrapper change. Consequently an unchanged scientific checker can still print
an absolute output filename to a generated stdout log. That display does not
change the mathematical result JSON. Distributing future raw logs requires
checking their displayed metadata separately.

No checker execution was performed during these packaging edits.
