fix(quality): type the 7 net-new 'as any' casts from #6292 (Lint red on the release tip)

#6292 rewrote/added zero-width-marker tests with 7 new 'as any' result casts,
pushing the file past its frozen suppression (84) — and when violations
exceed the suppressed count ESLint reports ALL of them, so the ci.yml Lint
job went red with 90 errors. The 7 new sites get typed shapes (delta /
arguments / choices / output accessors — same pattern as fecf888fd); the
pre-existing debt stays frozen at the exact new count (83). 50/50 tests
green, file lint-clean under the suppressions baseline.

config/quality/eslint-suppressions.json

@@ -1964,7 +1964,7 @@
   },
   "tests/unit/response-sanitizer.test.ts": {
     "@typescript-eslint/no-explicit-any": {
-      "count": 84
+      "count": 83
     }
   },
   "tests/unit/responses-parse-once-4041.test.ts": {

tests/unit/response-sanitizer.test.ts

@@ -898,7 +898,7 @@ test("sanitizeStreamingChunk strips zero-width joiners from native response.func
   const sanitized = sanitizeStreamingChunk({
     type: "response.function_call_arguments.delta",
     delta: '{"command":"o\u200d',
-  }) as any;
+  }) as unknown as { delta: string };
   const output = JSON.stringify(sanitized);
 
   assert.equal(sanitized.delta, '{"command":"o');
@@ -909,7 +909,7 @@ test("sanitizeStreamingChunk strips zero-width joiners from native response.func
   const sanitized = sanitizeStreamingChunk({
     type: "response.function_call_arguments.done",
     arguments: '{"command":"o\u200dpencode"}',
-  }) as any;
+  }) as unknown as { arguments: string };
   const output = JSON.stringify(sanitized);
 
   assert.equal(sanitized.arguments, '{"command":"opencode"}');
@@ -940,7 +940,9 @@ test("sanitizeStreamingChunk strips zero-width joiners from OpenAI chat tool-cal
         },
       },
     ],
-  }) as any;
+  }) as unknown as {
+    choices: { delta: { tool_calls: { function: { arguments: string } }[] } }[];
+  };
   const output = JSON.stringify(sanitized);
 
   assert.equal(
@@ -974,7 +976,9 @@ test("sanitizeOpenAIResponse strips zero-width joiners from non-stream tool-call
         },
       },
     ],
-  }) as any;
+  }) as unknown as {
+    choices: { message: { tool_calls: { function: { arguments: string } }[] } }[];
+  };
   const output = JSON.stringify(sanitized);
 
   assert.equal(
@@ -999,7 +1003,7 @@ test("sanitizeResponsesApiResponse strips zero-width joiners from native functio
         arguments: '{"command":"o\u200dpencode"}',
       },
     ],
-  }) as any;
+  }) as unknown as { output: { arguments: string }[] };
   const output = JSON.stringify(sanitized);
 
   assert.equal(sanitized.output[0].arguments, '{"command":"opencode"}');
@@ -1026,7 +1030,9 @@ test("sanitizer leaves normal tool arguments byte-identical (no parse/restringif
         },
       },
     ],
-  }) as any;
+  }) as unknown as {
+    choices: { delta: { tool_calls: { function: { arguments: string } }[] } }[];
+  };
   assert.equal(streamed.choices[0].delta.tool_calls[0].function.arguments === rawArgs, true);
 
   const nonStream = sanitizeOpenAIResponse({
@@ -1049,6 +1055,8 @@ test("sanitizer leaves normal tool arguments byte-identical (no parse/restringif
         },
       },
     ],
-  }) as any;
+  }) as unknown as {
+    choices: { message: { tool_calls: { function: { arguments: string } }[] } }[];
+  };
   assert.equal(nonStream.choices[0].message.tool_calls[0].function.arguments === rawArgs, true);
 });