fix(agents): harden Cloud Code Assist compatibility

- Expand schema scrubber to strip additional constraint keywords rejected
  by Cloud Code Assist (examples, minLength, maxLength, minimum, maximum,
  multipleOf, pattern, format, minItems, maxItems, uniqueItems,
  minProperties, maxProperties)
- Extend tool call ID sanitization to cover toolUse and toolCall block
  types (previously only functionCall was sanitized)
- Update pi-tools test to include 'examples' in unsupported keywords

Fixes 400 errors when using google-antigravity/claude-opus-4-5-thinking:
- tools.N.custom.input_schema: JSON schema is invalid
- messages.N.content.N.tool_use.id: String should match pattern

src/agents/pi-tools.test.ts

@@ -384,6 +384,7 @@ describe("createClawdbotCodingTools", () => {
       "$ref",
       "$defs",
       "definitions",
+      "examples",
     ]);
 
     const findUnsupportedKeywords = (