chore(lint): prune 3 obsolete eslint suppressions (#13359)

Merged. Your later commits (re-prune on the current base, then restoring the live `react-hooks/immutability` suppressions the first prune had wrongly dropped) were the right call, and they are carried intact.

Maintainer note: a repo-wide `eslint` run on today's release tip (the full validation for a suppressions prune) found **0 code errors** and only more entries that had gone stale since your base — the maintainer branch carries that same prune to the current tip on top of your commits. Removals only, nothing added.

Validated as a combined board first (this PR merged with the 21 siblings of the same wave on the release tip): eslint with the frozen suppressions, typecheck:core, check:open-sse-typecheck, complexity, cognitive-complexity, changelog-integrity, i18n new-key coverage, docs-counts, docs-sync, migration-numbering, provider-consistency and a duplicate-identifier audit all green, plus 176 passing / 0 failing focused node:test cases across the 25 test files the wave touches and the dashboard test under Vitest (2/0). Then re-validated alone on the fresh tip before this merge: conflicts re-resolved, file sizes rebaselined for this PR's own growth, eslint and this PR's focused tests re-run.

Thank you for chasing the false-positive prune to the end instead of leaving the live suppressions out.

config/quality/eslint-suppressions.json

@@ -608,11 +608,6 @@
       "count": 1
     }
   },
-  "open-sse/services/tlsClientBase.ts": {
-    "@typescript-eslint/no-unused-vars": {
-      "count": 1
-    }
-  },
   "open-sse/services/tokenLimitCounter.ts": {
     "@typescript-eslint/no-unused-vars": {
       "count": 1
@@ -931,11 +926,6 @@
       "count": 2
     }
   },
-  "src/app/(dashboard)/dashboard/providers/[id]/hooks/useProviderConnections.ts": {
-    "@typescript-eslint/no-unused-vars": {
-      "count": 1
-    }
-  },
   "src/app/(dashboard)/dashboard/providers/page.tsx": {
     "@typescript-eslint/no-unused-vars": {
       "count": 4
@@ -2705,7 +2695,7 @@
   },
   "tests/unit/build/check-licenses.test.ts": {
     "@typescript-eslint/no-explicit-any": {
-      "count": 5
+      "count": 4
     }
   },
   "tests/unit/bypass-handler.test.ts": {
@@ -2809,7 +2799,7 @@
   },
   "tests/unit/chatcore-translation-paths.test.ts": {
     "@typescript-eslint/no-explicit-any": {
-      "count": 31
+      "count": 30
     }
   },
   "tests/unit/check-docs-symbols.test.ts": {
@@ -3295,7 +3285,7 @@
   },
   "tests/unit/combo-routing-engine.test.ts": {
     "@typescript-eslint/no-explicit-any": {
-      "count": 268
+      "count": 267
     }
   },
   "tests/unit/combo-same-provider-cascade.test.ts": {