fix(external-sources): deduplicate configuration source presentation

[limityan]

Summary

• Coalesce provider-specific records that point to the same physical external configuration, while keeping older Peer Hosts fail-safe when they do not expose the new optional group identity.
• Hide healthy source groups with no imported Command, Tool, Subagent, MCP, or actionable diagnostic content; keep suppressed and unhealthy sources visible for recovery.
• Replace the misleading aggregate switch with compact capability-level controls, preserve scope disclosure, deduplicate diagnostics, and improve responsive/accessibility behavior.
• Keep suppressed OpenCode Subagent sources discoverable without parsing their content, and release the refresh gate before the post-mutation refresh to avoid self-deadlock.

Compatibility and risk

• presentationGroupId is optional, omitted when absent, and accepts legacy snapshots without the field.
• Existing single-source mutation commands are unchanged; no batch transport contract was added.
• Group identities are generated before path redaction from already-public stable source keys, so raw paths are not exposed.
• Older hosts without group identity keep records separate and source controls read-only according to existing host capabilities.

Validation

• pnpm --dir src/web-ui run test:run src/infrastructure/config/externalSourcePresentation.test.ts src/infrastructure/config/components/ExternalSourcesConfig.test.tsx (48 passed)
• pnpm run type-check:web
• pnpm run lint:web (0 errors; 13 existing warnings outside this change)
• cargo test -p bitfun-opencode-adapter --test opencode_subagent_adapter (5 passed)
• cargo test -p bitfun-product-domains --features product-full --test external_source_contracts presentation_group_id_is_optional_and_uses_the_camel_case_wire_name
• cargo test -p bitfun-core presentation_groups_are_assigned_before_location_redaction --lib
• cargo check -p bitfun-core --features product-full
• node scripts/check-core-boundaries.mjs
• pnpm run check:repo-hygiene
• git diff --check gcwing/main...HEAD
• Manual OpenCode CLI discovery of the local smoke Skill, Subagent, and Command fixtures

Independent review

A fresh architect review and a fresh product/UX review were completed after the implementation changes. Both found no remaining P0/P1; the product re-review also confirmed all follow-up P2 items were closed.