refactor: consolidate PNG encoder and safeParseJson utilities (#12457)

- Create shared PNG encoder module (src/media/png-encode.ts)

- Refactor qr-image.ts and live-image-probe.ts to use shared encoder

- Add safeParseJson to utils.ts and plugin-sdk exports

- Update msteams and pairing-store to use centralized safeParseJson

src/plugin-sdk/index.ts

@@ -229,7 +229,7 @@ export {
 } from "../agents/tools/common.js";
 export { formatDocsLink } from "../terminal/links.js";
 export type { HookEntry } from "../hooks/types.js";
-export { clamp, escapeRegExp, normalizeE164, sleep } from "../utils.js";
+export { clamp, escapeRegExp, normalizeE164, safeParseJson, sleep } from "../utils.js";
 export { stripAnsi } from "../terminal/ansi.js";
 export { missingTargetError } from "../infra/outbound/target-errors.js";
 export { registerLogTransport } from "../logging/logger.js";