fix(dashboard): correct the four guard-flag descriptions to the audited semantics

[woodsonl]

Summary

Follow-up to #15616. The feature-flag cards on the dashboard render the raw English description from src/shared/constants/featureFlagDefinitions.ts (the descriptionI18nKey values have no en.json message — verified, zero grep matches), and four of them still carried the pre-correction guard semantics that #15616 fixed in the docs:

• OUTBOUND_SSRF_GUARD_ENABLED said "Block outbound requests to private/internal IP ranges" — implying local/private URLs are blocked by default. It is a legacy alias whose dashboard toggle (a DB override) is read before the environment (fix(providers): read the SSRF Guard toggle from the dashboard, not only env #14172); false/0/no/off in either turns the host checks off like the private flag.
• OMNIROUTE_ALLOW_PRIVATE_PROVIDER_URLS said "Allow provider URLs pointing to private/internal networks" — it turns the host checks off (cloud-metadata block included) on the guard-mode paths and allows private webhook targets; the proxy-fallback test and webhook targets consult only this flag, so local/LAN hosts stay blocked there while it is off.
• OMNIROUTE_ALLOW_LOCAL_PROVIDER_URLS still said local models "need" this flag — it is the local-first default (on), and the metadata block covers all of 169.254.0.0/16 plus the known metadata hostnames.
• RERANK_REMOTE_PROVIDER_NODES ended with "(cloud-metadata hosts are never routed to)" — overstated: under guard mode none (private opt-in) the node check does not block metadata. The clause is dropped, matching the corrected FEATURE_FLAGS.md row.

No keys, defaults, or types change; description text only.

Tests Added Or Updated

tests/unit/feature-flag-descriptions-claims.test.ts — four tests pinning the corrected claims (legacy-alias semantics, metadata block scope, local-first default, no "never routed to" claim), so the dashboard text cannot drift back. All pass; the existing feature-flags-settings.test.ts (63 tests) stays green.

Validation

• node --import tsx/esm --test tests/unit/feature-flag-descriptions-claims.test.ts — 4/4.
• node --import tsx/esm --test tests/unit/feature-flags-settings.test.ts — 63/63 (the suite that asserts descriptionI18nKey wiring).
• npm run lint — 0 errors.
• No docs or .env changes → no docs gates in scope.

Reviewer Notes

⚠️ base-red inherited: #15306 (unit/integration/package-artifact ceiling hangs, vitest MCP-audit failure, ai-attribution lint error) — none traces to this diff. Depends on the corrected doc semantics from #15616 only for wording alignment; merges independently of it.