Fix coordsystem orphan parity + add schema patch layer + electrophys …

[neurolabusc]

…corpus

Core fixes (two real parity bugs):

• coordsystem.json orphan handling: replace the hardcoded EMG carve-out in SIDECAR_WITHOUT_DATAFILE with the general mechanism — build_associations now returns the fs-paths it resolved, and the caller marks them "viewed", mirroring Deno's walkBack side-effect. Orphaned coordsystem files are flagged for every modality; ones viewed by a recording's association walk are exempt.
• SpoilingType: add a parse-time schema patch layer (patches.rs) supplying the missing modality/extension selectors so the warning fires once on a DWI .nii.gz instead of triplicating across .bval/.bvec. Raw schema bytes stay verbatim (build.rs static tables and --schema byte-compare unaffected); a self-test fires when upstream fixes it, and a governance test guards against patches touching statically-emitted subtrees.

Tests/parity:

• Add electrophysiology parity coverage (eeg_face13, ieeg_epilepsy) fetched into gitignored data/ — the gap that let the coordsystem bug through. CTF-MEG (ds000246) excluded pending .ds-bundle handling.
• Promote EOG/MISC_CHANNEL_COUNT_MISMATCH into the RUST_CODES contract (Deno emits them too); update ISSUE_COVERAGE.md counts to match.
• Durable regression guard is the sidecar_without_datafile unit tests.

Docs:

• Reflow all tracked .md files to one line per paragraph (natural pagination).
• Fix YAML frontmatter break and a malformed README table cell; refresh stale build.rs/lib.rs/run.rs/test doc comments; bump status dates.
• audit_response.md: durable rationale store referenced by run.py divergences.