feat(rate): add regional-ground request file controls (#4273)

[d-sorgcodexagent]

Summary

• add stable contextual Open and Save As command IDs for seeded regional-ground variation requests
• React: strict 1 MiB v1 parser/canonical serializer, fatal UTF-8 import, transactional App-owner apply, accessible contextual actions, visible fail-closed feedback, and truthful browser download limitations
• PyQt6: narrow main-window/file-controller adapters, cancel-safe native dialogs, validate-before-apply Open, validate-before-dialog Save, and existing atomic native writer
• retain exact imported evidence until either owning editor changes; never save the untouched illustrative regional draft
• assert a shared Python-produced editor-qualified golden fixture in both runtimes
• no physics changes or illustrative fallback
• update SPEC, campaign manifest, and canonical handoffs in the implementation commit; a follow-up records the test-only pinned Ruff normalization

Verification

• React: 123 files / 782 tests; independent 28-test file-control subset; TypeScript; zero-warning ESLint; Vite production build
• Python/PyQt: 87 focused plus 25 follow-up; independent 67-test request/toolstrip/variation suite
• workflow-pinned Ruff 0.14.10 check/format, MyPy, manifest + 8 contracts, docs/governance/module-size/diff gates
• exact cross-runtime golden serialization assertion

Scope boundary

Browser download destination, overwrite, atomic replacement, recent-file access, and native-path semantics remain browser-owned and are disclosed. This slice does not invoke the ground pipeline or close #4273/#4267.

Refs #4273
Refs #4218
Refs #4267

[dieterolson]

Consolidated into #4410. Closing to reduce CI/CD runner load.