feat(region-filter): add configurable named region quick-pick groups #416

Context

Assessment baseline: dborup/CoreScope master 4a5ec5e231dd97ed7a4392e50e5f409f4dc5fab0 (13 October 2026). Recheck current master and competing work before implementation.

Operators could define convenient named groups of observer-region codes, so users can select common combinations in one action. Our current region filter also saves/renders programmatic setSelected changes without notifying page listeners, which must be addressed when wiring these controls.

Source for later comparison

Verified from GitHub's PR metadata and complete changed-file listing on 13 October 2026. The identifiers below are literal text, not hyperlinks or cross-repository references.

Source repository: Kpa-clawbot/CoreScope
Pull request number: 2170
PR head commit SHA: fced69a75970ae17785adfef12962b32fb8b676b
Upstream merged SHA (merge_commit_sha): 352a0ccd19896c5da6b5c821479444fdc8807cac
Files changed in this PR:
  - .github/workflows/deploy.yml
  - cmd/server/config.go
  - cmd/server/openapi.go
  - cmd/server/region_quick_picks_test.go
  - cmd/server/routes.go
  - config.example.json
  - docs/api-spec.md
  - public/region-filter.js
  - public/style.css
  - scripts/non-unit-tests.json
  - tests/e2e/test-region-quick-picks.js

Source repository: Kpa-clawbot/CoreScope
Pull request number: 2168
PR head commit SHA: 9e7327060ddcdb953f895ed4e092e363ad9e1c5c
Upstream merged SHA (merge_commit_sha): 99efaed33d48359d6a3bf189d87ce872f5fb0b36
Files changed in this PR:
  - public/region-filter.js
  - test-all.sh
  - tests/unit/test-region-filter-setselected.js

These are historical upstream comparison sources, not proof of equivalence with our fork and not a request to cherry-pick blindly. Recheck our current implementation and preserve fork-specific behavior.

Proposed work

• Add an optional bounded configuration/API representation of named groups; decide limits and unavailable-code handling explicitly.
• Preserve existing region selections and behavior when no groups are configured; keep region labels distinct from verified geographic boundaries.
• Ensure a real programmatic selection change notifies subscribers once and a no-op does not; avoid duplicate requests when clearing filters.
• Make quick picks keyboard/touch-accessible, themed and compatible with page-specific filtering and URL state.
• Test absent config, invalid/duplicate/unavailable codes, group limits, listener notifications, no-op selection, reset and restored URL/local state.

Acceptance criteria

Configured groups can be selected in one action without stale page data or duplicate refreshes, and installations without the option behave as before.

Scope

This issue records evaluation/follow-up work in our fork. It does not authorize deployment, production/staging changes, mail delivery, automatic key promotion or other external actions. Preserve fork-specific correctness, bounded work and the read-only measurement-server database contract; any separate account database exception requires explicit review.

Source performance numbers are not measurements of our deployment. Any claimed improvement requires our own benchmark and an independently reviewed implementation.